perm filename COMSCH.MSG[SCH,LSP]17 blob
sn#833013 filedate 1987-01-25 generic text, type C, neo UTF8
COMMENT ⊗ VALID 00230 PAGES
C REC PAGE DESCRIPTION
C00001 00001
C00039 00002
C00040 00003 ∂26-Apr-86 0738 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU The generality of define
C00042 00004 ∂26-Apr-86 1816 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@xx.lcs.mit.edu variata
C00048 00005 ∂27-Apr-86 1455 @MC.LCS.MIT.EDU:KMP@SCRC-STONY-BROOK.ARPA variata
C00057 00006 ∂27-Apr-86 1607 @MC.LCS.MIT.EDU:dcj%jacksun@SUN.COM SCOOPS, and GNU support question
C00060 00007 ∂28-Apr-86 1155 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: variata
C00066 00008 ∂28-Apr-86 1340 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: SCOOPS, and GNU support question
C00069 00009 ∂29-Apr-86 0743 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU meaning of *global* define
C00073 00010 ∂30-Apr-86 1425 @MC.LCS.MIT.EDU:jcm@ORNL-MSR.ARPA Questions from a newcomer
C00076 00011 ∂30-Apr-86 2156 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU Questions from a newcomer
C00078 00012 ∂05-May-86 1142 @MC.LCS.MIT.EDU:amn@LOCUS.UCLA.EDU getting C-Scheme running on HP workstations
C00080 00013 ∂05-May-86 1402 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU one more message about CScheme
C00082 00014 ∂05-May-86 1910 @MC.LCS.MIT.EDU:serafini@ames-aero implementation roundup
C00083 00015 ∂05-May-86 1914 JAR@MC.LCS.MIT.EDU implementation roundup
C00086 00016 ∂22-May-86 0819 NET-ORIGIN@MC.LCS.MIT.EDU H, E, S, B, O, D, X
C00088 00017 ∂22-May-86 0900 NET-ORIGIN@MC.LCS.MIT.EDU LOAD
C00093 00018 ∂22-May-86 1016 @MC.LCS.MIT.EDU:andy@aids-unix Re: LOAD
C00097 00019 ∂22-May-86 1558 @MC.LCS.MIT.EDU:KMP@ELEPHANT-BUTTE.SCRC.Symbolics.COM Notes about (↑ revised 3) report
C00103 00020 ∂23-May-86 0957 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: H, E, S, B, O, D, X
C00106 00021 ∂23-May-86 1013 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: LOAD
C00109 00022 ∂25-May-86 0923 @MC.LCS.MIT.EDU:VERACSD@USC-ISI.ARPA Addition to Mailing-List
C00111 00023 ∂25-May-86 1237 @MC.LCS.MIT.EDU:VERACSD@USC-ISI.ARPA Addition to Mailing-List
C00113 00024 ∂26-May-86 1555 @MC.LCS.MIT.EDU:JAR@MX.LCS.MIT.EDU R↑3RS draft
C00116 00025 ∂27-May-86 1120 NET-ORIGIN@MC.LCS.MIT.EDU Remaining questions & remarks (1)
C00128 00026 ∂27-May-86 1339 @MC.LCS.MIT.EDU:cth%indiana.csnet@CSNET-RELAY.ARPA define (resend)
C00132 00027 ∂27-May-86 1844 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU define (resend) (long)
C00140 00028 ∂28-May-86 0827 @MC.LCS.MIT.EDU,@KATHERINE.THINK.COM:gls@AQUINAS.THINK.COM Remaining questions & remarks (1)
C00142 00029 ∂28-May-86 0836 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA hash-consing
C00145 00030 ∂28-May-86 1137 @MC.LCS.MIT.EDU:andy@aids-unix Re: define
C00149 00031 ∂28-May-86 1241 @MC.LCS.MIT.EDU:dyb%indiana.csnet@CSNET-RELAY.ARPA Re: define (resend) (long) (short)
C00151 00032 ∂28-May-86 1736 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU define (resend) (long) (short)
C00157 00033 ∂28-May-86 2216 @MC.LCS.MIT.EDU:gls@Think.COM Embedded DEFINE forms
C00159 00034 ∂28-May-86 2243 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: Notes about (↑ revised 3) report
C00164 00035 ∂29-May-86 1417 NET-ORIGIN@MC.LCS.MIT.EDU define
C00170 00036 ∂29-May-86 1438 NET-ORIGIN@MC.LCS.MIT.EDU schedule
C00173 00037 ∂29-May-86 1450 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA define
C00176 00038 ∂29-May-86 1454 @MC.LCS.MIT.EDU:WAND%northeastern.edu@CSNET-RELAY.ARPA R3RS draft -- procedural
C00178 00039 ∂29-May-86 1545 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU R3RS draft -- procedural
C00180 00040 ∂29-May-86 1610 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA response to new draft report (long)
C00200 00041 ∂29-May-86 1610 @MC.LCS.MIT.EDU,@CSNET-RELAY.ARPA,@boethius.think.com:gls@AQUINAS.THINK.COM hash-consing
C00202 00042 ∂29-May-86 1706 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: global definitions
C00207 00043 ∂30-May-86 1432 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA definitions APPEND! etc
C00214 00044 ∂30-May-86 1650 @MC.LCS.MIT.EDU:OXLEY%ti-csl.csnet@CSNET-RELAY.ARPA Re: Embedded DEFINE forms
C00218 00045 ∂30-May-86 1703 @MC.LCS.MIT.EDU:WAND%northeastern.edu@CSNET-RELAY.ARPA procedure (Tnx)
C00219 00046 ∂30-May-86 1703 @MC.LCS.MIT.EDU:WAND%northeastern.edu@CSNET-RELAY.ARPA define -- a modest proposal
C00224 00047 ∂31-May-86 0108 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU define -- a modest proposal
C00229 00048 ∂31-May-86 0331 NET-ORIGIN@MC.LCS.MIT.EDU wanted: teaching do's and dont's
C00231 00049 ∂31-May-86 0539 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU wanted: teaching do's and dont's
C00237 00050 ∂31-May-86 0738 @MC.LCS.MIT.EDU:dyb%indiana.csnet@CSNET-RELAY.ARPA sentiments
C00244 00051 ∂31-May-86 1608 @MC.LCS.MIT.EDU:JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU sentiments
C00255 00052 ∂31-May-86 2319 @MC.LCS.MIT.EDU:JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU define -- a modest proposal
C00278 00053 ∂01-Jun-86 0815 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU define -- a modest proposal
C00288 00054 ∂01-Jun-86 2051 @MC.LCS.MIT.EDU:CPH@AI.AI.MIT.EDU schedule
C00290 00055 ∂01-Jun-86 2343 @MC.LCS.MIT.EDU:dyb%indiana.csnet@CSNET-RELAY.ARPA Re: sentiments
C00309 00056 ∂02-Jun-86 0730 @MC.LCS.MIT.EDU:JMILLER@OZ.AI.MIT.EDU Another Can of Worms?
C00313 00057 ∂02-Jun-86 1558 @MC.LCS.MIT.EDU:JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU sentiments
C00325 00058 ∂02-Jun-86 1604 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA DEFINE -- a concrete proposal
C00334 00059 ∂02-Jun-86 1803 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: definitions APPEND! etc
C00337 00060 ∂03-Jun-86 0853 @MC.LCS.MIT.EDU:Asrivastava%ti-csl.csnet@CSNET-RELAY.ARPA
C00339 00061 ∂03-Jun-86 0953 @MC.LCS.MIT.EDU:JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU APPEND!
C00341 00062 ∂03-Jun-86 1010 @MC.LCS.MIT.EDU:JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU portability
C00349 00063 ∂03-Jun-86 1124 @MC.LCS.MIT.EDU:WAND%northeastern.edu@CSNET-RELAY.ARPA define
C00352 00064 ∂03-Jun-86 1441 @MC.LCS.MIT.EDU:Asrivastava%ti-csl.csnet@CSNET-RELAY.ARPA SCOOPS source
C00354 00065 ∂03-Jun-86 1554 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Is BEGIN primitive?
C00357 00066 ∂03-Jun-86 2023 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU ftp-able r3rs.dvi
C00359 00067 ∂04-Jun-86 0554 @MC.LCS.MIT.EDU:JMILLER@OZ.AI.MIT.EDU Re: portability
C00361 00068 ∂04-Jun-86 1049 @MC.LCS.MIT.EDU:Asrivastava%ti-csl.csnet@CSNET-RELAY.ARPA Re: SCOOPS source
C00363 00069 ∂04-Jun-86 1623 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: portability
C00366 00070 ∂05-Jun-86 0546 @MC.LCS.MIT.EDU:JMILLER@OZ.AI.MIT.EDU Re: portability
C00368 00071 ∂05-Jun-86 0935 @MC.LCS.MIT.EDU:dfried%indiana.csnet@CSNET-RELAY.ARPA Will's proposal
C00369 00072 ∂05-Jun-86 0939 @MC.LCS.MIT.EDU:dfried%indiana.csnet@CSNET-RELAY.ARPA named-lambda and rec
C00370 00073 ∂05-Jun-86 1055 @MC.LCS.MIT.EDU:CPH@AI.AI.MIT.EDU named-lambda and rec
C00372 00074 ∂06-Jun-86 0800 @MC.LCS.MIT.EDU:JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU portability
C00377 00075 ∂06-Jun-86 0806 @MC.LCS.MIT.EDU:dfried%indiana.csnet@CSNET-RELAY.ARPA add1 and sub1
C00379 00076 ∂06-Jun-86 1039 @MC.LCS.MIT.EDU:CPH@AI.AI.MIT.EDU add1 and sub1
C00381 00077 ∂06-Jun-86 2038 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: portability
C00385 00078 ∂07-Jun-86 1658 @MC.LCS.MIT.EDU:dfried%indiana.csnet@CSNET-RELAY.ARPA macros.
C00386 00079 ∂07-Jun-86 1820 @MC.LCS.MIT.EDU:adams%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: named-lambda and rec
C00388 00080 ∂07-Jun-86 1829 @MC.LCS.MIT.EDU:dyb%indiana.csnet@CSNET-RELAY.ARPA Re: add1 and sub1
C00390 00081 ∂08-Jun-86 1652 @MC.LCS.MIT.EDU:Swenson.Multics@MIT-MULTICS.ARPA Re: SCOOPS source
C00392 00082 ∂09-Jun-86 1643 @MC.LCS.MIT.EDU:JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU portability
C00399 00083 ∂10-Jun-86 0744 @MC.LCS.MIT.EDU:dyb%indiana.csnet@CSNET-RELAY.ARPA Re: portability
C00403 00084 ∂11-Jun-86 1021 @MC.LCS.MIT.EDU:TIM%upenn.csnet@CSNET-RELAY.ARPA Scheme for AI based CAI
C00410 00085 ∂11-Jun-86 1145 @MC.LCS.MIT.EDU:FAHLMAN@C.CS.CMU.EDU Scheme for AI based CAI
C00415 00086 ∂13-Jun-86 0956 @MC.LCS.MIT.EDU:mmeyer%tilde%ti-csl.csnet@CSNET-RELAY.ARPA Revised↑3 Draft Comment
C00417 00087 ∂15-Jun-86 1251 @MC.LCS.MIT.EDU:cth%indiana.csnet@CSNET-RELAY.ARPA Logic Continuations (Abstract)
C00420 00088 ∂17-Jun-86 1621 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Number syntax
C00424 00089 ∂17-Jun-86 1909 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Number syntax
C00427 00090 ∂17-Jun-86 1912 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Policy on change-making
C00431 00091 ∂18-Jun-86 2144 @MC.LCS.MIT.EDU:dyb%indiana.csnet@CSNET-RELAY.ARPA Re: Number syntax
C00433 00092 ∂20-Jun-86 0202 @MC.LCS.MIT.EDU:JINX@OZ.AI.MIT.EDU Policy on change-making
C00435 00093 ∂23-Jun-86 1412 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Bibliography
C00437 00094 ∂26-Jun-86 2114 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Remaining questions & remarks (2)
C00459 00095 ∂27-Jun-86 0943 @MC.LCS.MIT.EDU:ramsdell%linus@mitre-bedford.ARPA r3rs presentation
C00465 00096 ∂27-Jun-86 1115 @MC.LCS.MIT.EDU:gls@Think.COM Remaining questions & remarks (2)
C00470 00097 ∂27-Jun-86 1653 @MC.LCS.MIT.EDU:SGR@ELEPHANT-BUTTE.SCRC.Symbolics.COM [INGRIA@G.BBN.COM: Scheme for LISPM]
C00472 00098 ∂27-Jun-86 1930 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU typo
C00473 00099 ∂27-Jun-86 2142 @MC.LCS.MIT.EDU:dfried%indiana.csnet@CSNET-RELAY.ARPA Grandfathering Responses
C00492 00100 ∂28-Jun-86 1511 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU variable vs. identifier
C00494 00101 ∂28-Jun-86 1511 @MC.LCS.MIT.EDU:dfried%indiana.csnet@CSNET-RELAY.ARPA Grandfathering response
C00513 00102 ∂29-Jun-86 1205 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU [INGRIA@G.BBN.COM: Scheme for LISPM]
C00516 00103 ∂29-Jun-86 2140 @MC.LCS.MIT.EDU:dyb%indiana.csnet@CSNET-RELAY.ARPA Re: Remaining questions & remarks (2)
C00527 00104 ∂30-Jun-86 0741 @MC.LCS.MIT.EDU:dyb%indiana.csnet@CSNET-RELAY.ARPA Re: r3rs presentation (long)
C00536 00105 ∂01-Jul-86 1040 @MC.LCS.MIT.EDU:ramsdell%linus@mitre-bedford.ARPA Call-with-current-continuation
C00540 00106 ∂01-Jul-86 1432 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: Remaining questions & remarks (2)
C00555 00107 ∂01-Jul-86 1446 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: Remaining questions & remarks (2)
C00577 00108 ∂02-Jul-86 0515 @MC.LCS.MIT.EDU:JMILLER@OZ.AI.MIT.EDU Re: Remaining questions & remarks (2)
C00579 00109 ∂02-Jul-86 0557 @MC.LCS.MIT.EDU:ramsdell%linus@mitre-bedford.ARPA Call-with-current-continuation
C00583 00110 ∂02-Jul-86 1652 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Remaining questions & remarks (2)
C00586 00111 ∂07-Jul-86 0929 @MC.LCS.MIT.EDU:VERACSD@A.ISI.EDU CL Compatiblity Package
C00588 00112 ∂07-Jul-86 1254 @MC.LCS.MIT.EDU:cth%indiana.csnet@CSNET-RELAY.ARPA votes and things
C00594 00113 ∂08-Jul-86 0538 @MC.LCS.MIT.EDU:dyb%indiana.csnet@CSNET-RELAY.ARPA display and write-char
C00596 00114 ∂08-Jul-86 2347 @MC.LCS.MIT.EDU:WAND%northeastern.edu@CSNET-RELAY.ARPA remaining questions & remarks (2)
C00602 00115 ∂09-Jul-86 0340 @MC.LCS.MIT.EDU:HAL%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU mitch wand's comments
C00603 00116 ∂10-Jul-86 1015 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU number syntax
C00608 00117 ∂10-Jul-86 1016 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU call-with-*put-file --> call-with-*put-port
C00610 00118 ∂10-Jul-86 1228 @MC.LCS.MIT.EDU:MICHAEL@CS.COLUMBIA.EDU How big would a "minimal" scheme interpreter be?
C00611 00119 ∂10-Jul-86 1300 @MC.LCS.MIT.EDU:andy@sun3.ads.ARPA My comments on the R↑RS
C00630 00120 ∂10-Jul-86 1313 @MC.LCS.MIT.EDU:MICHAEL@CS.COLUMBIA.EDU [Michael van Biema <MICHAEL@CS.COLUMBIA.EDU>: How big would a "minimal" scheme interpreter be?]
C00633 00121 ∂10-Jul-86 1342 @MC.LCS.MIT.EDU:wagle%iuvax.indiana.edu@CSNET-RELAY.ARPA Re: Remaining questions & remarks (2)
C00637 00122 ∂10-Jul-86 1540 @MC.LCS.MIT.EDU:andy@sun3.ads.ARPA My answers to your thirty questions on R↑RS
C00647 00123 ∂10-Jul-86 1941 @MC.LCS.MIT.EDU:whill%hplabsc@hplabs.HP.COM Re: [Michael van Biema <MICHAEL@CS.COLUMBIA.EDU>: How big would a "minimal" scheme interpreter be?]
C00649 00124 ∂11-Jul-86 0336 @MC.LCS.MIT.EDU:bc@MEDIA-LAB.MIT.EDU MacScheme
C00651 00125 ∂11-Jul-86 0925 @MC.LCS.MIT.EDU:gls@Think.COM My comments on the R↑RS
C00660 00126 ∂11-Jul-86 0935 @MC.LCS.MIT.EDU:cscott@bfly-vax.bbn.com tiny scheme
C00662 00127 ∂11-Jul-86 1142 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: My comments on the R↑RS
C00668 00128 ∂11-Jul-86 1642 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU test
C00669 00129 ∂12-Jul-86 1837 @MC.LCS.MIT.EDU:RPG@SU-AI.ARPA Compatibility with Common Lisp: A meta comment
C00674 00130 ∂13-Jul-86 1528 @MC.LCS.MIT.EDU:andy@sun3.ads.ARPA Scheme's DO construct
C00690 00131 ∂14-Jul-86 0252 @MC.LCS.MIT.EDU:adams%tekchips.tek.csnet@CSNET-RELAY.ARPA Flaws of form
C00697 00132 ∂14-Jul-86 0325 @MC.LCS.MIT.EDU:adams%tekchips.tek.csnet@CSNET-RELAY.ARPA Flaws of form
C00704 00133 ∂14-Jul-86 0641 @MC.LCS.MIT.EDU:OXLEY%ti-csl.csnet@CSNET-RELAY.ARPA Re: Compatibility with Common Lisp: A meta comment
C00706 00134 ∂14-Jul-86 0741 @MC.LCS.MIT.EDU:ramsdell%linus@mitre-bedford.ARPA Common Lisp
C00709 00135 ∂14-Jul-86 1008 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU [ANDY: dedication]
C00711 00136 ∂14-Jul-86 1337 @MC.LCS.MIT.EDU:RPG@SU-AI.ARPA Use of DO in Common Lisp Code
C00715 00137 ∂14-Jul-86 1448 @MC.LCS.MIT.EDU:goodhart%cod@nosc.ARPA Scheme Request
C00717 00138 ∂14-Jul-86 1514 @MC.LCS.MIT.EDU:andy@sun3.ads.ARPA Scheme vs. Common Lisp, #1: Politics
C00731 00139 ∂14-Jul-86 1607 @MC.LCS.MIT.EDU:RPG@SU-AI.ARPA Politics
C00736 00140 ∂14-Jul-86 1702 @MC.LCS.MIT.EDU:dyb%iuvax.indiana.edu@CSNET-RELAY.ARPA call-with-xput-port vs. call-with-xput-file
C00741 00141 ∂14-Jul-86 1814 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Scheme Request
C00744 00142 ∂14-Jul-86 2156 @MC.LCS.MIT.EDU:dyb%iuvax.indiana.edu@CSNET-RELAY.ARPA the colon (:) in identifier syntax
C00746 00143 ∂14-Jul-86 2159 @MC.LCS.MIT.EDU:dyb%iuvax.indiana.edu@CSNET-RELAY.ARPA exp versus expt
C00748 00144 ∂15-Jul-86 0951 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU convergence
C00750 00145 ∂15-Jul-86 1807 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: Scheme's DO construct
C00761 00146 ∂15-Jul-86 2019 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU rrrs-authors
C00765 00147 ∂15-Jul-86 2105 @MC.LCS.MIT.EDU:jleech@sun6.ads the rrrs authors
C00767 00148 ∂16-Jul-86 1731 @MC.LCS.MIT.EDU:brooks%tilde%TI-CSL.CSNET@CSNET-RELAY.ARPA Substring & friends
C00770 00149 ∂16-Jul-86 1732 @MC.LCS.MIT.EDU:Bartley%TI-CSL.CSNET@CSNET-RELAY.ARPA Re: number syntax
C00779 00150 ∂16-Jul-86 1921 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU July 15 draft sent
C00781 00151 ∂17-Jul-86 0851 @MC.LCS.MIT.EDU:CPH@AI.AI.MIT.EDU Substring & friends
C00784 00152 ∂17-Jul-86 1217 @MC.LCS.MIT.EDU:GJS%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU Re: Substring & friends
C00786 00153 ∂17-Jul-86 1412 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU [jtv%fingate.bitnet: Scheme Request]
C00788 00154 ∂17-Jul-86 1442 @MC.LCS.MIT.EDU:adams%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: Substring & friends
C00791 00155 ∂18-Jul-86 0012 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: Substring & friends
C00794 00156 ∂18-Jul-86 1428 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU [jtv%fingate.bitnet: Scheme Request]
C00796 00157 ∂21-Jul-86 0448 @MC.LCS.MIT.EDU:ramsdell%linus@mitre-bedford.ARPA typos
C00799 00158 ∂21-Jul-86 0737 @MC.LCS.MIT.EDU:Mike←Wilson%CARLETON.BITNET@WISCVM.WISC.EDU Performance and Evaluation of Scheme Systems...
C00802 00159 ∂21-Jul-86 0808 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU schedule
C00805 00160 ∂21-Jul-86 0827 @MC.LCS.MIT.EDU:CLOWNEY@BLUE.RUTGERS.EDU Logic Continuations (Abstract)
C00807 00161 ∂21-Jul-86 1014 @MC.LCS.MIT.EDU:gls@Think.COM Scheme's DO construct
C00811 00162 ∂21-Jul-86 1057 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: Performance and Evaluation of Scheme Systems...
C00815 00163 ∂21-Jul-86 1143 @MC.LCS.MIT.EDU:bc@MEDIA-LAB.MIT.EDU Bobcat scheme
C00817 00164 ∂21-Jul-86 1228 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Logic Continuations (Abstract)
C00834 00165 ∂21-Jul-86 1325 @MC.LCS.MIT.EDU:gls@Think.COM Re: Scheme's DO construct
C00836 00166 ∂21-Jul-86 1357 @MC.LCS.MIT.EDU:YEKTA@AI.AI.MIT.EDU Bobcat scheme
C00838 00167 ∂22-Jul-86 0710 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU title wars
C00841 00168 ∂22-Jul-86 0717 @MC.LCS.MIT.EDU:HAL%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU title wars
C00842 00169 ∂22-Jul-86 1143 @MC.LCS.MIT.EDU:CPH@AI.AI.MIT.EDU title wars
C00844 00170 ∂22-Jul-86 1157 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU title wars
C00846 00171 ∂22-Jul-86 1243 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: title wars
C00848 00172 ∂22-Jul-86 1252 @MC.LCS.MIT.EDU,@YALE-BULLDOG.ARPA:hudak@YALE.ARPA Re: Performance and Evaluation of Scheme Systems...
C00854 00173 ∂22-Jul-86 1529 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: title wars
C00857 00174 ∂22-Jul-86 1755 @MC.LCS.MIT.EDU:GJS%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU title
C00858 00175 ∂24-Jul-86 1244 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU call-with-xput-port vs. call-with-xput-file
C00863 00176 ∂25-Jul-86 0022 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: July 15 draft sent
C00872 00177 ∂25-Jul-86 1026 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: number syntax
C00881 00178 ∂25-Jul-86 1127 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU (eqv? #e1 #i1)
C00884 00179 ∂25-Jul-86 1346 @MC.LCS.MIT.EDU:ramsdell%linus@mitre-bedford.ARPA July 15th draft
C00890 00180 ∂26-Jul-86 2137 @MC.LCS.MIT.EDU:cth%iuvax.indiana.edu@CSNET-RELAY.ARPA corrections and suggestions
C00898 00181 ∂28-Jul-86 0810 @MC.LCS.MIT.EDU:ramsdell%linus@mitre-bedford.ARPA Fault logic in eq? comment
C00901 00182 ∂28-Jul-86 1616 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: corrections and suggestions
C00907 00183 ∂29-Jul-86 1331 @MC.LCS.MIT.EDU:dyb@iuvax.indiana.edu critical problems with call---file, with---file
C00914 00184 ∂29-Jul-86 1423 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU schedule
C00917 00185 ∂29-Jul-86 1814 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: critical problems with call---file, with---file
C00922 00186 ∂31-Jul-86 0732 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU rrrs authors meeting, lunch Tuesday
C00925 00187 ∂31-Jul-86 1111 @MC.LCS.MIT.EDU:fateman@DALI.BERKELEY.EDU Re: Performance and Evaluation of Scheme Systems...
C00927 00188 ∂04-Aug-86 0107 @MC.LCS.MIT.EDU:facility%cantuar.waterloo.edu@CSNET-RELAY.ARPA
C00929 00189 ∂04-Aug-86 0158 @MC.LCS.MIT.EDU:facility%cantuar.waterloo.edu@CSNET-RELAY.ARPA
C00931 00190 ∂06-Aug-86 0150 @MC.LCS.MIT.EDU:facility%cantuar.waterloo.edu@CSNET-RELAY.ARPA
C00933 00191 ∂07-Aug-86 0136 @MC.LCS.MIT.EDU:JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU non-list arguments
C00936 00192 ∂07-Aug-86 0301 @MC.LCS.MIT.EDU:Pase@DOCKMASTER.ARPA Scheme for the Atari ST
C00938 00193 ∂07-Aug-86 0730 @MC.LCS.MIT.EDU:jcm@ORNL-MSR.ARPA Re: Scheme for the Atari ST
C00942 00194 ∂08-Aug-86 0819 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU
C00947 00195 ∂08-Aug-86 1230 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU [Masinter.pa: synonym streams..]
C00949 00196 ∂08-Aug-86 1712 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA "Final" comments on RRRRS
C00952 00197 ∂11-Aug-86 0855 @MC.LCS.MIT.EDU,@MIT-MULTICS.ARPA:SRAUCH@UNBMVS1.BITNET Instructor's manual for S&ICP by Julie Sussman
C00954 00198 ∂13-Aug-86 0238 NET-ORIGIN@MC.LCS.MIT.EDU Re: define
C00957 00199 ∂14-Aug-86 1728 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Minutes from lunch 5 August 1986
C00967 00200 ∂14-Aug-86 1855 @MC.LCS.MIT.EDU:ANDY@Sushi.Stanford.EDU Re: Minutes from lunch 5 August 1986
C00969 00201 ∂14-Aug-86 2053 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA substring indexes
C00972 00202 ∂14-Aug-86 2233 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA r-cubed syntax (nits)
C00975 00203 ∂15-Aug-86 0902 @MC.LCS.MIT.EDU:dyb%iuvax.indiana.edu@CSNET-RELAY.ARPA Re: Minutes from lunch 5 August 1986
C00976 00204 ∂15-Aug-86 1106 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU r-cubed syntax (nits)
C00979 00205 ∂15-Aug-86 1112 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU scheme report tar file
C00981 00206 ∂15-Aug-86 1223 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU "Final" comments on RRRRS
C00985 00207 ∂15-Aug-86 2150 @MC.LCS.MIT.EDU:CPH@AI.AI.MIT.EDU "Final" comments on RRRRS
C00989 00208 ∂18-Aug-86 0051 @MC.LCS.MIT.EDU:ram@YALE.ARPA Re: The generality of define
C00994 00209 ∂18-Aug-86 1650 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA define syntax (an apology)
C00998 00210 ∂20-Aug-86 2002 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA numbers
C01006 00211 ∂22-Aug-86 0555 @MC.LCS.MIT.EDU:dyb%iuvax.indiana.edu@CSNET-RELAY.ARPA a few more comments
C01010 00212 ∂22-Aug-86 1208 @MC.LCS.MIT.EDU,@SEBASTIAN.THINK.COM:gls@AQUINAS.THINK.COM 1986 Lisp conference bibliography
C01049 00213 ∂23-Aug-86 1738 @MC.LCS.MIT.EDU:GJS%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU Re: numbers
C01051 00214 ∂25-Aug-86 2008 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Another nit my favorite numbers
C01056 00215 ∂28-Aug-86 0849 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU Minutes from lunch 5 August 1986
C01058 00216 ∂28-Aug-86 0908 @MC.LCS.MIT.EDU:mhwu%hplmhw@hplabs.HP.COM Minutes/Standardize Graphics
C01060 00217 ∂28-Aug-86 2012 @MC.LCS.MIT.EDU:GJS%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU Re: Minutes from lunch 5 August 1986
C01062 00218 ∂29-Aug-86 1503 @MC.LCS.MIT.EDU:andy@ads.ARPA graphics for Scheme
C01067 00219 ∂02-Sep-86 1519 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU substring-vector-null-fill!, colitis, etc.
C01075 00220 ∂03-Sep-86 0424 @MC.LCS.MIT.EDU:ramsdell%faron@mitre-bedford.ARPA call-with-xxput-port
C01077 00221 ∂03-Sep-86 0625 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU substring-vector-null-fill!, colitis, etc.
C01081 00222 ∂04-Sep-86 0858 @MC.LCS.MIT.EDU:F95THOMP%CARLETON.BITNET@WISCVM.WISC.EDU Scheme Books?
C01083 00223 ∂04-Sep-86 1828 @MC.LCS.MIT.EDU:wecker%cookie.DEC@decwrl.DEC.COM Please delete me from this distribution list, thanks - dave
C01084 00224 ∂05-Sep-86 1947 @MC.LCS.MIT.EDU:mh@BU-CS.BU.EDU list
C01085 00225 ∂08-Sep-86 0330 @MC.LCS.MIT.EDU:shneider%cui.unige.chunet%ubc.csnet@CSNET-RELAY.ARPA Beginners question: Advising methods in TI scheme
C01088 00226 ∂08-Sep-86 0826 @MC.LCS.MIT.EDU:philbin-jim@YALE.ARPA Re: [THOMAS: Scheme Books?]
C01090 00227 ∂08-Sep-86 0848 @MC.LCS.MIT.EDU:carr%utah-orion@utah-cs.arpa scoops
C01092 00228 ∂08-Sep-86 1334 @MC.LCS.MIT.EDU:shneider%cui.unige.chunet%ubc.csnet@CSNET-RELAY.ARPA Beginners question: Advising methods in TI scheme
C01095 00229 ∂08-Sep-86 1509 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Good & bad news
C01098 00230 ∂08-Sep-86 1614 @MC.LCS.MIT.EDU:wagle%iuvax.indiana.edu@CSNET-RELAY.ARPA substring-vector-null-fill!, coliti
C01100 ENDMK
C⊗;
∂26-Apr-86 0738 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU The generality of define
Received: from MC.LCS.MIT.EDU by SU-AI.ARPA with TCP; 26 Apr 86 07:38:32 PST
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Date: 26 Apr 1986 10:38 EST (Sat)
Message-ID: <JINX.12201925541.BABYL@MIT-OZ>
From: Bill Rozas <JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>
To: andy@AIDS-UNIX.ARPA (Andy Cromarty)
Cc: SCHEME@MC.LCS.MIT.EDU
Subject: The generality of define
In-reply-to: Msg of 23 Apr 1986 19:09-EST from andy at aids-unix (Andy Cromarty)
(define square (lambda (x) (* x x)))
at all, but rather to
(define square (rec square (lambda (x) (* x x))))
The new version of RRRS changes this.
(define (square x) (* x x))
will be equivalent to
(define square (lambda (x) (* x x)))
The self recursive form can be obtained by explicitely using LETREC or
wRECk.
∂26-Apr-86 1816 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@xx.lcs.mit.edu variata
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Date: 26 Apr 1986 10:33 EST (Sat)
Message-ID: <JINX.12201924643.BABYL@MIT-OZ>
From: Bill Rozas <JINX%OZ.AI.MIT.EDU@xx.lcs.mit.edu>
To: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
Cc: JAR%mc.lcs.mit.edu@CSNET-RELAY.ARPA,
RRRS-AUTHORS%mc.lcs.mit.edu@CSNET-RELAY.ARPA
Subject: variata
In-reply-to: Msg of 25 Apr 1986 19:04-EST from David Bartley <Bartley%ti-csl.csnet at CSNET-RELAY.ARPA>
To summarize:
-- We agree that (ELSE) is a no-no and that (COND) and (COND (ELSE exp))
are valid.
-- I feel that (BEGIN) should have the same meaning as (COND), but I
won't push the point.
I don't like this. Unfortunately JAR did not give me choice c (status
quo, where (COND (ELSE ...)) is legal, but (COND) is not), which I
like best. I object pretty strongly to (BEGIN) and somewhat less
strongly to (COND). The usual rationale is that it makes macros
easier to write, but this is just laziness of the same sort as using
(cdr (assq <something> <some-list>)) in a Lisp where (cdr '()) -> '().
(COND (ELSE ...)) although silly has a clear meaning (unless the ELSE
clause is empty, which should be an error, but we agree on this).
-- We agree on using EQV? for CASE.
I like JAR's proposal too.
-- We agree that (EQV? "" "") and (EQV? #() #()) are true, but I worry
about confusion when I mix Scheme and Common LISP programs.
I'm worried about gratuitous differences between EQ? and EQV?. I
would object (although not terribly strongly) to making
(eq? '#() '#()) be #T, but I think it is silly to have EQ? and EQV?
behave differently on this. The reason I object to (eq? '#() '#())
being #T is that inline coding of make-vector would become more
expensive. Make-vector is very cheap in our implementation and a good
candidate for inline coding (although we don't currently do it), and
having it intern 0 length vectors (strings) would make it more
expensive.
-- I like warning messages for things like (MAKE-VECTOR 0 exp) more
than you do. We can probably agree to provide declarations so you
won't refuse to buy my system!
I agree with JAR. I think that (MAKE-VECTOR 0 exp) is reasonable and
no error (warning) message should be given. I don't understand why
you object to it. Why not warn about reversing a list with less than 2
elements also?
-- I'm not apologetic about trying to avoid ``gratuitous''
differences with Common LISP, but I don't want to burden the
description of Scheme with constant references to it either.
I agree. Unless there is strong reason to do otherwise, we should not
differ from Common Lisp. This should probably be stated early (if we
all agree, of course), and assumed afterwards. A reference to this
remark in various places might be appropriate.
∂27-Apr-86 1455 @MC.LCS.MIT.EDU:KMP@SCRC-STONY-BROOK.ARPA variata
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Date: Sun, 27 Apr 86 17:55 EDT
From: Kent M Pitman <KMP@SCRC-STONY-BROOK.ARPA>
Subject: variata
To: JAR@MIT-MC.ARPA
cc: RRRS-AUTHORS@MIT-MC.ARPA
In-Reply-To: <[MC.LCS.MIT.EDU].895280.860425.JAR>
References: The message of 24 Apr 86 10:43-EST from Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
Message-ID: <860427175526.2.KMP@HUMMINGBIRD.SCRC.Symbolics.COM>
I am absolutely opposed to making (COND) or (COND (ELSE)) or (BEGIN) or
(LAMBDA ()) illegal. I am content to make them return undefined values but
I insist that, for example, (LAMBDA () (BEGIN) 3) is a completely well-formed
expression that should neither cause the compiler to say anything nor cause
an error at runtime.
I am very opposed to requiring ELSE to be the last clause in a COND. It seems
to me that
(COND ((FOO)) (ELSE #T) ((BAR)))
is like like
(OR (FOO) #T (BAR)).
I hope no one is going to insist that the previous form should also be illegal
and/or that it should be warned about by a compiler. The call to BAR is
obviously not going to get reached for pragmatic reasons, but there may be
legitimate situations where program-writing programs could want to construct
something like this and I think we'd be shooting ourselves in the foot to
disallow such things. Also, I think it tends to make the grammar look more
graceful if ELSE can occur anyway. The particular case of interest is:
`(COND ,@FORMS (ELSE FOO))
where FORMS may be allowed to contain an ELSE clause. I object to having to
write:
`(COND ,@FORMS ,@(IF (AND FORMS (NOT (EQ (CAR (LAST FORMS)) 'ELSE)))
`((ELSE FOO))
`()))
If you decide to make any of the above forms legal, I wish to have my
reasons for disagreement cited.
I think CASE should be changed to use EQUAL?, which I think is in agreement
with a recent suggestion by you. This will get around a lot of confusion that
could otherwise result from the recent trend toward wanting to intern quoted
structure.
I'm fairly satisfied with the way things seem to be going in the EQ? and
EQV? discussion so will mostly decline from any comment for now on that
subject.
JAR: If people believe that it's important to be able to parse Scheme's
read syntax using only standard Common Lisp reader features, then by all
means we must allow (eq? '#() '#()) to be false, but we also have to
change the syntax of numbers, and make colon not be a constituent
character. But Scheme's eqv? could still deal with #() and "" as I
propose even if eq? doesn't.
Right.
JAR: It looks like I'll lose on this point, so I won't push it too hard.
I'm just resisting adding yet another clause which basically says "we
did this for compatibility with Common Lisp."
I am sympathetic to this position.
I strongly oppose requiring APPEND to do gratuitous copying. It's trivial to
adopt
Bartley (about APPEND): ... I'd like some discussion on this. It sounds
like something a LISP programmer could trip up on, especially those
who use (APPEND X '()) to copy X. Steele's book specifically mentions
that APPEND will work that way in Common LISP, but implies that it is
poor style. My inclination is to be compatible with Common LISP in
order to minimize frustration for the poor people we're trying to
win over to Scheme.
JAR: If this is what other people want I'm happy with it too (except
again for the fact that I'll have to insert another apology and another
reference to Common Lisp).
The fact that CL provides COPY-LIST is enough for me. I am strongly opposed
to continuing this lossage of forcing APPEND to do gratuitous copying. You're
falling down on your let's-not-be-gratuitously-compatible-with-CL maxim. CL
itself is really only doing it for compatibility, too. This is a case where
we're clearly right and ought not give in.
JAR: What about (let ((x (list 'a))) (eq? x (reverse x))) ?
Bartley: I feel strongly that REVERSE should always copy (unless its
argument is the empty list), since it is easier to remember that rule
than that it does so only when there's more than one element in the list.
Pragmatically, I often do something like (APPEND! (REVERSE X) Y), and
wouldn't want to side effect the original list in X if it had exactly
one element. (Note that this works correctly when X is the empty
list, so this is a pretty unusual boundary condition.)
JAR: I agree. (Except note that it doesn't copy empty lists....)
I am receptive to the idea of permitting the result of REVERSE to share with
its input. The idiom (APPEND! (REVERSE X) Y) should just be named. CL has
REVAPPEND and NRECONC. I believe we should just have APPEND-REVERSE and
APPEND-REVERSE! which do these common operations. This would reduce the need
to rely on copying. I think we should take a consistent stand on the idea
that REVERSE, APPEND, do not have to copy and that that's why we provide
COPY-LIST. People can always write their own COPY-LIST-REVERSE,
COPY-LIST-APPEND, etc. if they really need to intertwine the two operations
for some efficiency reason. The dumb routines are so easy to write yourself,
after all. The ones provided by the system should be the messy-to-write
super-optimizing ones.
∂27-Apr-86 1607 @MC.LCS.MIT.EDU:dcj%jacksun@SUN.COM SCOOPS, and GNU support question
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Date: Sun, 27 Apr 86 16:04:02 PDT
From: dcj%jacksun@SUN.COM (Donald Clark Jackson)
Message-Id: <8604272304.AA11217@jacksun.sun.uucp>
To: scheme@mc.lcs.mit.edu
Subject: SCOOPS, and GNU support question
As a user of TI-SCHEME, I kind of like
the SCOOPS object-oriented package.
I have C-Scheme running on a Sun now, and
I would like to get SCOOPS running on it.
Is source for SCOOPS available, or is it
TI proprietary code? Is there something
similar available?
Also, while getting the "inferior scheme"
mode in GNU Emacs to work, I had to change the
following line in xscheme.el:
(make-shell "scheme" scheme-program-name nil "-emacs")
to
(make-shell "scheme" scheme-program-name)
What was the "-emacs" supposed to do?
I have GNU Emacs Version 17.61, and
MIT C-Scheme Version 6.1.
If this is the wrong mailing list for these
questions, please suggest a better forum.
Mail me your replies, if possible. I'll
summarize to this list if there is any
demand.
Thanks,
Don Jackson
djackson@sun.com
{ucbvax,decwrl,...}!sun!djackson
∂28-Apr-86 1155 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: variata
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Date: Mon 28 Apr 86 13:28:11-CDT
From: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: Re: variata
To: JINX%OZ.AI.MIT.EDU%xx.lcs.mit.edu@CSNET-RELAY.ARPA
Cc: JAR%mc.lcs.mit.edu@CSNET-RELAY.ARPA,
RRRS-AUTHORS%mc.lcs.mit.edu@CSNET-RELAY.ARPA,
Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
In-Reply-To: <JINX.12201924643.BABYL@MIT-OZ>
Message-Id: <12202480652.63.BARTLEY@CSC60>
>Date: 26 Apr 1986 10:33 EST (Sat)
>From: Bill Rozas <JINX%OZ.AI.MIT.EDU%xx.lcs.mit.edu@csnet-relay>
>
> [Bartley:]
> -- I like warning messages for things like (MAKE-VECTOR 0 exp) more
> than you do. We can probably agree to provide declarations so you
> won't refuse to buy my system!
>
>I agree with JAR. I think that (MAKE-VECTOR 0 exp) is reasonable and
>no error (warning) message should be given. I don't understand why
>you object to it. Why not warn about reversing a list with less than 2
>elements also?
I'm not objecting, just asking questions to clarify JAR's position and
to elicit comments from others with strong opinions. Let's see if I
can clarify both mine and yours:
-- I agree that (MAKE-VECTOR EXP1 EXP2) shouldn't be an error or
cause a warning at runtime should EXP1 evaluate to zero. I'm talking
about compile-time warnings (e.g. for a COMPILE-FILE) when EXP1 is a
literal zero. I oppose most, perhaps all, warnings during evaluation.
Sorry I wasn't more explicit -- I tend to think in terms of separate
compilation and I'm sure many of you are thinking primarily in terms
of interpretation.
-- Likewise, (REVERSE EXP3) obviously shouldn't cause a warning when
EXP3 evaluates to a list with fewer than two elements. But a
compile-time warning about (REVERSE '(A)) might be helpful (if it
weren't so unlikely!).
There's no real debate here. If I were to report `warnings,' as
opposed to actual `errors,' I'd do it only in a compilation mode where
they wouldn't be confused with the runtime behavior of the program and
only if the user asked for them by setting a flag. This is a
development environment issue, not a language issue.
> -- We agree that (ELSE) is a no-no and that (COND) and (COND (ELSE exp))
> are valid.
>
> -- I feel that (BEGIN) should have the same meaning as (COND), but I
> won't push the point.
>
>I don't like this. Unfortunately JAR did not give me choice c (status
>quo, where (COND (ELSE ...)) is legal, but (COND) is not), which I
>like best. I object pretty strongly to (BEGIN) and somewhat less
>strongly to (COND). The usual rationale is that it makes macros
>easier to write, but this is just laziness of the same sort as using
>(cdr (assq <something> <some-list>)) in a Lisp where (cdr '()) -> '().
>(COND (ELSE ...)) although silly has a clear meaning (unless the ELSE
>clause is empty, which should be an error, but we agree on this).
Actually, JINX and I seem to agree that (BEGIN) and (COND) are equally
meaningless. I offer to allow (COND) but feel (BEGIN) makes as much
sense. If there's a consensus against (COND), then I'm even happier.
I'm not all that motivated by wanting to write lazy macros or program-
generating programs for reasons similar to JINX's.
Regards,
David Bartley
-------
∂28-Apr-86 1340 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: SCOOPS, and GNU support question
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Date: Mon 28 Apr 86 13:42:05-CDT
From: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: Re: SCOOPS, and GNU support question
To: dcj%jacksun%sun.com@CSNET-RELAY.ARPA,
scheme%mc.lcs.mit.edu@CSNET-RELAY.ARPA
Cc: Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
In-Reply-To: <8604272304.AA11217sun.sun.uucp>
Message-Id: <12202483182.63.BARTLEY@CSC60>
> Date: Sun, 27 Apr 86 16:04:02 PDT
> From: Donald Clark Jackson <dcj%jacksun%sun.com@CSNET-RELAY.ARPA>
>
> As a user of TI-SCHEME, I kind of like
> the SCOOPS object-oriented package.
> I have C-Scheme running on a Sun now, and
> I would like to get SCOOPS running on it.
>
> Is source for SCOOPS available, or is it
> TI proprietary code? Is there something
> similar available?
I'll look into getting formal approval from our product group to
release the source for SCOOPS. The actual SCOOPS source for TI's PC
Scheme has some implementation-dependent efficiency hacks built in,
but we may be able to put together a sanitized portable version.
However, SCOOPS is built upon first-class environments, so it wouldn't
port to some dialects out there (including the standard).
If we get permission to give out the source, we will of course want to
make it non-proprietary, which works both ways: you owe us nothing and
we owe you nothing (well, very little!). I'll see what we can work
out and post the result.
David Bartley
-------
∂29-Apr-86 0743 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU meaning of *global* define
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Date: 29 Apr 1986 10:20 EDT (Tue)
Message-ID: <JINX.12202697723.BABYL@MIT-OZ>
From: Bill Rozas <JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>
To: willc%tekchips%tektronix.csnet@CSNET-RELAY.ARPA
Cc: JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU, RRRS-Authors%mit-mc@XX.LCS.MIT.EDU
Subject: meaning of *global* define
In-reply-to: Msg of 15 Apr 1986 15:49-EST from willc%tekchips%tektronix.csnet at CSNET-RELAY.ARPA
What is the difference between having incorrect procedures all over
the place and having incorrect numbers, lists, strings, or vectors all
over the place?
It would be possible to fix other objects if in our system all objects
maintained a history of how they were created, and often I think that
this would be a very nice debugging environment. Unfortunately, for
efficiency reasons, they do not. Procedures, fortunately, contain the
environments where they are closed, and these include most of the
relevant information about their creation history. By modifying these
environments we can patch a running system in a way we cannot patch it
if the "wrong value" happens to be a vector or other "simple" data
structure. Just because we cannot provide a more general and powerful
debugging tool, it does not mean that we should not provide an
extremely useful (the most useful to me) special case.
In terms of implementation, there are various possible trade offs. I
can easily accept a system where incremental definition (when it does
not degenerate into assignment) causes a garbage-collection-like
process to occur to make all the references consistent. I am
perfectly willing to pay the price of a very powerful feature which I
use relatively often.
PS: Sorry about taking so long to answer this message. It was buried
in a large pile.
∂30-Apr-86 1425 @MC.LCS.MIT.EDU:jcm@ORNL-MSR.ARPA Questions from a newcomer
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id AA16413; Wed, 30 Apr 86 16:38:46 edt
Date: Wed, 30 Apr 86 16:38:46 edt
From: jcm@ORNL-MSR.ARPA (James A. Mullens)
Message-Id: <8604302038.AA16413@ORNL-MSR.ARPA>
To: scheme@mc
Subject: Questions from a newcomer
Hi -
I would like to learn know about an implementation of Scheme which runs
on VAX VMS 4.x and an implementation which runs on a 68000 machine
(especially Amiga, Macintosh Plus, Sage/Stride, or Atari 1040ST). I
have seen a reference to Scheme 312 which sounded interesting.
I have also seen a reference to "Chez Scheme" for VAX BSD 4.2++ which I
would like to know more about.
I am especially interested "native" implementations (not implemented on
top of another Lisp), versions with a compiler, and versions which are
public domain. I have purchased TI's PC Scheme for my IBM AT.
I am interested in Scheme because I think it may run reasonably well on
a micro I can afford to have at home. I have a Sage II now, but I am
considering another 68000 machine. I am also hoping that Scheme will
be a simple, easy to implement Lisp which is not thundering towards
commercialization.
I tried Golden Common Lisp on ATs and was disappointed in the
unwieldiness.
We have Common Lisp (DEC Lisp and NIL) on the VAXen I use at work,
but I would like to investigate Scheme as an alternative.
- Thanks
jim mullens
oak ridge national laboratory
∂30-Apr-86 2156 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU Questions from a newcomer
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Date: 1 May 1986 00:43 EDT (Thu)
Message-ID: <JINX.12203116956.BABYL@MIT-OZ>
From: Bill Rozas <JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>
To: jcm@ORNL-MSR.ARPA (James A. Mullens)
Cc: scheme@MC.LCS.MIT.EDU
Subject: Questions from a newcomer
In-reply-to: Msg of 30 Apr 1986 16:38-EDT from jcm at ORNL-MSR.ARPA (James A. Mullens)
MIT CScheme runs on a wide variety of machines with C compilers. In
particular it runs on some 68000 systems (mostly unices) and on VMS.
It currently does not have a compiler, but will have one by the end of
the summer (the VAX back end may not be ready at that time, however).
It is public domain.
∂05-May-86 1142 @MC.LCS.MIT.EDU:amn@LOCUS.UCLA.EDU getting C-Scheme running on HP workstations
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Date: Mon, 5 May 86 11:26:40 PDT
From: Arthur Newman <amn@LOCUS.UCLA.EDU>
To: scheme@mc.lcs.mit.edu
Subject: getting C-Scheme running on HP workstations
Message-ID: <860505.182640z.03031.amn@ZEUS.LOCUS.UCLA.EDU>
By just installing the student version we would get the following bug:
trying to set! an undefined variable would cause a bus error and kick
you out of Scheme back to the system prompt.
I recompiled Scheme using the normal.bin file, and eval'ed
(enable-language-features). Now trying to set! undefined variables
just gives an error message.
Are there any reasons why we had trouble with set! in the student system
that you can think of?
Thanks for any help,
Arthur Newman
∂05-May-86 1402 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU one more message about CScheme
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Date: 5 May 1986 16:26 EDT (Mon)
Message-ID: <JINX.12204337135.BABYL@MIT-OZ>
From: Bill Rozas <JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>
To: scheme@MC.LCS.MIT.EDU
Subject: one more message about CScheme
Please, send bug reports about MIT CScheme to
bug-cscheme%oz@mit-mc, not to this (scheme@mit-mc) mailing list.
bug-scheme%oz@mit-mc is not good either. There is more than one
implementation at MIT, and bug-scheme does not refer to CScheme.
General questions about CScheme should be sent to
info-cscheme%oz@mit-mc.
Thanks.
PS: When answering bug reports incorrectly sent to this mailing list I
have tried not to send the reply here. If you have run across similar
bugs, and have not received a reply, send mail to bug-cscheme, since
they have probably been fixed. Notices of bug fixes, etc, are sent to
info-cscheme.
∂05-May-86 1910 @MC.LCS.MIT.EDU:serafini@ames-aero implementation roundup
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Date: 5 May 86 18:32:00 PST
From: DAVE SERAFINI <serafini@ames-aero>
Subject: implementation roundup
To: scheme <scheme@mit-mc.arpa>
Reply-To: DAVE SERAFINI <serafini@ames-aero>
Has anyone compiled a list of the various implementations of scheme extant,
and could I be send a copy?
advTHANKSance
Dave Serafini
------
∂05-May-86 1914 JAR@MC.LCS.MIT.EDU implementation roundup
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Date: Mon, 5 May 86 22:12:44 EDT
From: Jonathan A Rees <JAR@MC.LCS.MIT.EDU>
Subject: implementation roundup
To: serafini@AMES-AERO.ARPA
cc: SCHEME@MC.LCS.MIT.EDU
In-reply-to: Msg of 5 May 86 18:32:00 PST from DAVE SERAFINI <serafini at ames-aero>
Message-ID: <[MC.LCS.MIT.EDU].904409.860505.JAR>
Date: 5 May 86 18:32:00 PST
From: DAVE SERAFINI <serafini at ames-aero>
Has anyone compiled a list of the various implementations of scheme extant,
and could I be send a copy?
There's a list of implementations, with brief descriptions, in the file
"SCHEME;SCHEME IMPLS" on MIT-MC. I compiled it from messages sent to
this mailing list. I don't think MC's FTP server requires passwords to
log in; if you are asked to supply a user name or password, give
arbitrary strings like GUEST and ARPA.
People who don't have Internet access and want a copy of this file
should send a message to JAR@MC (not to SCHEME@MC!) requesting it. I'll
batch requests, except that if I get more than ten requests I'll simply
send the file out to the entire Scheme mailing list. It's about 12K
bytes so I'll have to mail it in two pieces (MC's mailer is limited to
10 or 11K).
Jonathan
∂22-May-86 0819 NET-ORIGIN@MC.LCS.MIT.EDU H, E, S, B, O, D, X
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Date: Thu, 22 May 86 11:18 EDT
From: Jonathan A Rees <JAR@MIT-AI.ARPA>
Subject: H, E, S, B, O, D, X
To: rrrs-authors@MIT-MC.ARPA
Message-ID: <"860522111800.2.jar@AI"@JOE-LOUIS.LCS.MIT.EDU>
Has anyone implemented number output formats in their entirety? A
number of people have requested the the following minor change: that
the keywords which are now single letters be spelled out. E.g.
EXPRESSED and SUPPRESSED instead of E and S.
We can discuss the details separately. If some people think such a
change is a bad idea at this point then the change shouldn't be made.
But if no one has implemented it and people like the idea then I think
it can be done pretty painlessly.
The letters in question are H, E, S, B, O, D, and X. If you don't know
what they mean that simply attests to the desirability of spelling them
out.
Jonathan
∂22-May-86 0900 NET-ORIGIN@MC.LCS.MIT.EDU LOAD
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Date: Thu, 22 May 86 11:51 EDT
From: Jonathan A Rees <JAR@MIT-AI.ARPA>
Subject: LOAD
To: rrrs-authors@MIT-MC.ARPA
Message-ID: <"860522115129.3.jar@AI"@JOE-LOUIS.LCS.MIT.EDU>
I would like to either remove LOAD from the report or change the way in
which it is presented.
Reasons:
(a) A LOAD procedure is equipotent with EVAL, and EVAL isn't documented.
The same reasons that applied to kick out EVAL apply here.
(b) It seems to me a perfectly reasonable idea to create Scheme systems
that don't have a LOAD procedure. I can imagine at least two completely
different kinds of implementations in which LOAD wouldn't make sense.
One kind of implementation would be in the style of most implementations
of PASCAL, FORTRAN, etc., where one runs programs by configuring entire
environments at once. This avoids all the semantic stickiness of LOAD
and EVAL by making configuration a meta-issue. Second, at the opposite
extreme, in an Interlisp-like implementation where one actually edits
"in core", and files don't generally come into play, LOAD is pretty
meaningless.
(c) It seems to me that LOAD is a user interface/programming environment
issue. We don't talk about read-eval-print loops, or entering or
exiting scheme, or logging in, or editing files; how is this different?
Alternative solutions:
(1) Omit it entirely without saying anything.
(2) Mention somewhere (e.g. in the introduction) that Scheme is
"usually" an interactive language with a read-eval-print loop and
support for things like interactive debugging and dynamic program
loading.
(3) Reclassify LOAD as being part of the syntax of a file. I.e., like
DEFINE, it can only occur at top level in a file.
(4) Leave it alone, but put it in a "user interface" section along with
TRANSCRIPT-ON and TRANSCRIPT-OFF (and maybe TRACE, DEBUG, and EDIT?),
instead of classifying it as an input procedure. Make a disclaimer that
these things are only guaranteed to work "at top level" (whatever that
is).
(5) Some combination of (3) and (4) [allow it both in files and at
command loops].
Feedback solicited.
-Jonathan
-----
KMP: please send a message making a case for a (LOAD-SILENTLY x).
∂22-May-86 1016 @MC.LCS.MIT.EDU:andy@aids-unix Re: LOAD
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Date: Thu, 22 May 86 10:13:20 pdt
From: andy@aids-unix (Andy Cromarty)
To: JAR@MIT-AI.ARPA
Subject: Re: LOAD
Cc: rrrs-authors@mit-mc
1. Numbers: I agree with full naming. Even when I was actively working
on a full numbers package I couldn't remember what these were
wiuthout looking them up. Perhaps implementations should be free
to support single-letter names in "not recommended" status for
the sake of downward compatibility.
2. LOAD: This is sticky. The beast probably should not exist in this
or any other language, because files themselves are a bad idea
left over from the early days of computer science when we didn't
know any better and allowed hardware to dominate software design.
The problem is that not having LOAD available requires that we
have an alternative available, which means either (a) having a
transparent or essentially transparent object filing system or (b)
having a non-transparent object filing system with an explicit
object-writing operator (e.g. WRITE or some variant would have to
be able to render permanent any arbitrary object, such as functions
that make lexical reference to variables from an enclosing scope
and similar LISP objects that can have very messy state in a
lexically scoped environment).
If we have LOAD available but we don't document it, we have simply
ignored the problem, rather than either solving it or admitting we
can't yet. The fact is that, unlike EVAL, LOAD is something that
everyone will have to use, including newcomers; it's not esoterica,
even if it does interfere with intellectual cleanliness. The means
to address such cleanliness issues is probably design, not selective
non-documentation.
A good compromise might be to add a paragraph of comment,
something like what appears in the RRRS for macros, stating that
this is currently a difficult area in LISP design and that LOAD
is provided but that work on alternatives (e.g. object filing systems)
is encouraged.
asc
∂22-May-86 1558 @MC.LCS.MIT.EDU:KMP@ELEPHANT-BUTTE.SCRC.Symbolics.COM Notes about (↑ revised 3) report
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Date: Thu, 22 May 86 18:53 EDT
From: Kent M Pitman <KMP@SCRC-STONY-BROOK.ARPA>
Subject: Notes about (↑ revised 3) report
To: JAR@MIT-MC.ARPA
cc: KMP@SCRC-STONY-BROOK.ARPA, RRRS-AUTHORS@MIT-MC.ARPA
Message-ID: <860522185327.2.KMP@RIO-DE-JANEIRO.SCRC.Symbolics.COM>
On p30, while reading the description of READ, the following questions
occurred to me, the answers to which are in some cases probably dependent
upon the answers to the others in order to assure useful consistency:
* Does the stream become closed as a side-effect of hitting eof?
* Is it an error to read from a closed stream, or does eof just keep
getting returned?
* Can you read the eof object twice at the end of a file using READ ?
How about if using READ-CHAR ? PEEK-CHAR ?
* Is it possible to detect whether a file is closed?
* Is it acceptable for close on certain streams to not really close the file?
For example, I could imagine implementing terminal streams or streams into
editor buffers in a way such that they just always claimed to be open and
close was a no-op.
Also on p30, it seems to me that the notion of CHAR-READY? is not a useful one.
It's subject to timing errors in multi-processed systems and/or systems which
allow asynchronous interrupts. The Lisp Machine's TYI-NO-HANG paradigm is much
better, since it has a more test-and-set feel to it and is more easy to use
reliably. I suggest that CHAR-READY? should be flushed and replaced by a
READ-CHAR? which returns either a character if one is ready, or NIL otherwise.
This gets you out of the bind with rubbing out stuff that CHAR-READY? has
noticed, which is really an awful crock. I believe that TYI-NO-HANG will
interact satisfactorily with Lispm-style rubout handlers.
On p30, the issue with LOAD is that if we're going to define it, we need to give
it a standard meaning so it can be usefully used on different systems. If we
don't say it either types out or doesn't, then people can't use it in their
programs for fear it will screw up the display (this exact problem arose in real
situations in my work with Common Lisp). I feel that a LOAD which does
no typeout is a useful interface to the operating system and a necessary
feature for bootstrapping other code. The absence to provide it will mean that
either every user will have to type in a definition of load at the keyboard
or every system will have to provide it anyway. Obviously, this translates
to that every system will provide one, since no one's going to force the user
to type it in. If every system is going to provide it, we might as well
standardize on it so people can know what they're getting. If particular
dialects want to offer additional options, well, ... you're no doubt aware
of my feelings on this issue and i'll spare the cc'd folks for now.
∂23-May-86 0957 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: H, E, S, B, O, D, X
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Date: Fri 23 May 86 10:06:06-CDT
From: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: Re: H, E, S, B, O, D, X
To: JAR%ai.ai.mit.edu@CSNET-RELAY.ARPA,
rrrs-authors%mc.lcs.mit.edu@CSNET-RELAY.ARPA
Cc: Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
In-Reply-To: <"860522111800.2.jar@AI"@JOE-LOUIS.LCS.MIT.EDU>
Message-Id: <12208997463.23.BARTLEY@CSC60>
We have implemented the number output formats in PC Scheme. I like
the idea of spelling out the keywords and won't "vote" against it, but
there are two troublesome aspects:
(1) We already have a product out that supports the abbreviated style,
so we'd have to grandfather it. That's always a minor pain.
(2) My experience is that not one programmer in ten can spell both
EXPRESSED and SUPPRESSED correctly (sorry about that!). What should
NUMBER->STRING do with EXPRESED or SUPRESSED? [Of course, there are
plenty of other opportunities for misspellings to trip one up!]
Seriously, I recommend that we retain the single letter abbreviations
as an option if we switch to full names for these keywords.
Regards,
David Bartley
-------
∂23-May-86 1013 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: LOAD
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Date: Fri 23 May 86 09:54:59-CDT
From: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: Re: LOAD
To: JAR%ai.ai.mit.edu@CSNET-RELAY.ARPA,
rrrs-authors%mc.lcs.mit.edu@CSNET-RELAY.ARPA
Cc: Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
In-Reply-To: <"860522115129.3.jar@AI"@JOE-LOUIS.LCS.MIT.EDU>
Message-Id: <12208995440.23.BARTLEY@CSC60>
My first thought is that LOAD should be retained, but not as an
essential procedure. That would help a programmer avoid some name
conflicts, since most implementations of Scheme and Lisp have a LOAD.
My second thought is to wonder why we have included non-essential
procedures in the Report. Is it to warn a programmer that the given
identifier should be considered "reserved" or is it to guide
implementors toward consistent extensions to the essential language?
In the first case, I'd say that the programmer should be referring
primarily to the manual for his implementation, not to the Report, and
that that manual should take care to warn him of portability issues.
In the second case, I'd say that our coverage of "suggested"
extensions is so patchy that it's almost irrelevant whether LOAD is
mentioned or not. After all, where are COMPILE and EVAL, two obvious
names for extended features?
So, my inclination is to let JAR do whatever he likes. This is a
pragmatic issue. Ideally, we'd have an appendix that discusses these
things, but that may be Pandora's box.
--db--
-------
∂25-May-86 0923 @MC.LCS.MIT.EDU:VERACSD@USC-ISI.ARPA Addition to Mailing-List
Received: from MC.LCS.MIT.EDU by SU-AI.ARPA with TCP; 25 May 86 09:23:11 PDT
Received: from USC-ISI.ARPA by MC.LCS.MIT.EDU 25 May 86 12:18:59 EDT
Date: 25 May 1986 12:18-EDT
Sender: VERACSD@USC-ISI.ARPA
Subject: Addition to Mailing-List
From: VERACSD@USC-ISI.ARPA
To: scheme@MC.LCS.MIT.EDU
Cc: veracsd@USC-ISI.ARPA
Message-ID: <[USC-ISI.ARPA]25-May-86 12:18:05.VERACSD>
Please add me to your Scheme Mailing-List.
I am presently running MacScheme, and have used it to work
through the examples in the Abelson & Sussman book, define a
Common Lisp compatibility package, and implement a PROLOG.
I am particularly interested in using continuations and macros in
Scheme. I have a great general interest in logic-programming,
and the imple- mentation of logic-programming languages.
Thanks.
-- Cris Kobryn
∂25-May-86 1237 @MC.LCS.MIT.EDU:VERACSD@USC-ISI.ARPA Addition to Mailing-List
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Date: 25 May 1986 12:18-EDT
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Subject: Addition to Mailing-List
From: VERACSD@USC-ISI.ARPA
To: scheme@MC.LCS.MIT.EDU
Cc: veracsd@USC-ISI.ARPA
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ReSent-To: scheme@MC.LCS.MIT.EDU
ReSent-From: VERACSD at USC-ISI.ARPA
ReSent-Date: 25 May 1986
Please add me to your Scheme Mailing-List.
I am presently running MacScheme, and have used it to work
through the examples in the Abelson & Sussman book, define a
Common Lisp compatibility package, and implement a PROLOG.
I am particularly interested in using continuations and macros in
Scheme. I have a great general interest in logic-programming,
and the imple- mentation of logic-programming languages.
Thanks.
-- Cris Kobryn
∂26-May-86 1555 @MC.LCS.MIT.EDU:JAR@MX.LCS.MIT.EDU R↑3RS draft
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Date: Mon, 26 May 86 18:54:00 EDT
From: Jonathan A Rees <JAR@MX.LCS.MIT.EDU>
Subject: R↑3RS draft
To: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <[MX.LCS.MIT.EDU].921583.860526.JAR>
I have mailed / given out copies of the latest draft of the report (22
May). People in Boston and New Haven should have either received one
from me or should stop by and pick one up. A copy went to Tektronix by
special courier. People with Internet access AND Latex AND something
that will read Unix "tar" files should FTP to MIT-PREP, using user
Scheme and null password if necessary, and get the file
"/u/jar/r3rs.tar". If FTP doesn't seem to work, then try telnetting to
PREP and logging in as Scheme (no password needed). The login shell is
FTP. Send the abovementioned file to your machine. Extract all the
files somewhere and run Latex on the file "rrrs.tex". If you don't have
something that will read tar files, use FTP to get all the files on the
directory /u/jar/r3rs.
On Friday I mailed one copy to Dan Friedman and one copy to Dave
Bartley, so people at Indiana and TI should get extra copies from them.
Anyone else who wants one mailed should let me know right away (although
I think that everyone has been taken care of).
There is a cover letter, too, relevant parts of which I'll send
electronically.
Jonathan.
∂27-May-86 1120 NET-ORIGIN@MC.LCS.MIT.EDU Remaining questions & remarks (1)
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Date: Tue, 27 May 86 14:19 EDT
From: Jonathan A Rees <JAR@MIT-AI.ARPA>
Subject: Remaining questions & remarks (1)
To: rrrs-authors@MIT-MC.ARPA
Message-ID: <"860527141917.1.jar@AI"@ROCKY-GRAZIANO.LCS.MIT.EDU>
I included the following with the reports I sent and gave out. Here it
is again for those people who don't have it already. It enumerates most
of the remaining nits I have. Don't be intimidated by the number of
items; none are serious. Many of these questions have been discussed
and some have been resolved already. For those items that stay
unresolved, I'll take the conservative position and leave the new report
in agreement with the old report.
I'll send a second, more recent set of nits separately.
- Jonathan
-----
Questions on LANGUAGE
I left CASE as is, using EQV? as the comparison, and I explicitly stated
that the object ought to be boolean, character, number, or symbol. But
shouldn't it allow empty lists, vectors, and strings, too?
May structure be shared in cases like (APPEND '(A B) '()) , or should APPEND
be Common Lisp compatible? [Bartley says sharing would be a gratuitous
incompatibility with CL, I'm invlined to agree.]
Should APPEND and APPEND! explicitly allow any object as last argument
(CL compatible)?
Should APPEND! disallow () as other than last argument?
I decided that allowing GCD, etc. of Gaussian integers was probably
premature. I'll put them in if someone writes the documentation
(including examples).
Can we decide on what to do about number exactness on input? How about:
inexact if there are digits following a decimal point, or if exponential
notation is used. Otherwise exact.
Can we specify that DISPLAY of a character does the same thing as
WRITE-CHAR?
What should be said, if anything, about the desirability and/or legality
of EQUAL? failing to terminate? Rozas thinks an implementation with
this property is in error.
In light of the vagaries of CALL-WITH-xxPUT-FILE, perhaps it
would be a good idea to explicitly state that closing a closed port
should be a no-op instead of an error.
-----
Questions on PRESENTATION
Should the various examples which use DEFINE be changed to use the
(define (foo ...) ...) syntax instead of (define foo (lambda ...))?
Several people have told me that all those LAMBDA's could unnecessarily
intimidate SIGPLAN readers.
There are two places (in descriptions of let* and letrec) where it is
necessary to create a lambda body in a context (such as the tail of a
BEGIN) where there isn't one already. What is the cleanest way to do
this? Is (let () ...) ok, or would ((lambda () ...)) or something else
be better?
Is the word ``promise'' all right for objects returned by DELAY?
Should the complete presentation of FORCE appear up front with DELAY, or
delayed until the place where the entry for FORCE appears?
-----
Notes on LANGUAGE
The selectors in a CASE expression must be distinct.
I have left CASE and COND syntax as in RRRS: there must be at least one
clause, but it may be an ELSE clause.
BOOLEAN? is essential.
No agreement on COND or BEGIN. I have left them as in RRRS.
[To do: fix the BNF to agree!]
The RRRS explicitly allows internal definitions in the body of a LETREC.
They are scoped to the body only, not to the entire expression. I can
flush this "feature" if a movement arises to do so; it seems sufficient
to me to permit only expressions (not definitions) in the body.
The list to which the rest argument gets bound must be newly allocated.
Making LET* be essential was suggested, but there was resistance to
this, so I left it as is.
There was strong sentiment both for removing REC and for removing
NAMED-LAMBDA. However, the sentiment was not unanimous. I don't
understand why it should have matterred so much, since neither is an
essential feature. If these are present, shouldn't everyone's favorite
features be present too? ... Supporters of REC included Kent Dybvig and
Dan Friedman. Supporters of NAMED-LAMBDA included Jim Miller and Henry
Wu. In addition, Bill Rozas insisted that if REC stayed, then
NAMED-LAMBDA must stay too, but he was willing to see both go.
APPEND! necessarily clobbers its arguments (other than the last and
empty ones).
Many people wanted the number predicates pruned (i.e. choose between <
and <?). No agreement here, so both stay.
The BNF says that ALL random symbols, including ELSE, =>, UNQUOTE, and
UNQUOTE-SPLICING, are reserved and may not be used as variable names. I
hope this is OK with everyone.
Note that the grammar for numbers allows one to write things like 23##
for inexact numbers. This was implicit in last summer's report, and I
thought it wouldn't make sense if this was allowed on output but not on
input.
The case sensitivity issue was a very sensitive one (so to speak). I
did not change the report's stance of symbol case insensitivity.
-----
Notes on PRESENTATION
I listed myself as "editor" of this version. I probably should just
remain a coauthor, but the report needs an editor in order to look like
the Algol 60 report.
I eliminated the term ``special form.'' I introduced phrases like ``IF
expression'' in a couple of places; things like IF and CASE are not
referred to as active agents (keywords don't refer to particular
things---it's the evaluator that actively interprets expressions having
certain special syntactic forms). I removed statements like
``<expression> is evaluated but <variable> is not.''
At Pitman's request, I changed ``guard'' to ``test'' in the description
of COND because ``guard'' has inappropriate connotations; COND doesn't
really implement a Dijkstra guarded conditional.
The term "variable" now refers the name itself, not the binding or the
location. This is in accordance with the way logicians (including
Alonzo Church) use the term.
I decided not to add an appendix describing S&ICP differences. The most
important difference, I think, was RRRS's lack of DELAY and FORCE. I no
longer find the presence of SEQUENCE distasteful.
I removed the apologetic statement that went with the description of T
and NIL. (Some people actually like T and NIL.)
The sentence ``This procedure can be very confusing if used
indiscriminately'' in the descriptions of set-car! and set-cdr! was
struck at Chris Hanson's request; it seemed gratuitous.
There are at least sixteen different references to Common Lisp. I'm
going to try to remove some of them. We have to make it very clear that
Scheme is 11 years old and originated some of CL's ideas --- not the
other way around!
∂27-May-86 1339 @MC.LCS.MIT.EDU:cth%indiana.csnet@CSNET-RELAY.ARPA define (resend)
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Date: Tue, 27 May 86 12:20:15 EST
From: Chris Haynes <cth%indiana.csnet@CSNET-RELAY.ARPA>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: define (resend)
We have one great difficulty with the RRRS as it stands: DEFINE can not make
global bindings when used locally and still be consistent with the report.
Much has been said about the pros and cons of the "MIT style" local define,
and it is clear that a consensus is not possible, so a compromise is in
order. Simply making MIT style optional is not acceptible: optional syntax,
if implemented, must conform to a single semantics. Thus DEFINE semantics is
preempted as the report is currently written.
Using a different keyword, such as DEFINE-GLOBAL, to make global definitions
from lexically nested positions is not acceptible to us. We have tried to
live with such arrangements for some months now, and have found them
intolerable.
A compromise position would be to include a form such as DEFINE-GLOBAL in
the report, hopefully as a required special form, and make an explicit
exception in the case of DEFINE to the rule that optional features, if
implemented, always have a single semantics. The idea is that it should be
possible, in any "standard" Scheme that supports some kind of macro package,
to get *either* style of lexical DEFINE by simply loading the appropriate
macro package. Failing that, it should at least be *possible* for a
Scheme implementation to provide such packages, and allow either package to
be loaded without stepping outside of the "standard".
This compromise is not something that anyone would love, but it is most
sincerely hoped that it is something that everyone can live with. Then
no one will feel bad about being associated with the RRRS.
Chris Haynes
Dan Friedman
Kent Dybvig
∂27-May-86 1844 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU define (resend) (long)
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Date: 27 May 1986 21:43 EDT (Tue)
Message-ID: <JINX.12210162108.BABYL@MIT-OZ>
From: Bill Rozas <JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>
To: Chris Haynes <cth%indiana.csnet@CSNET-RELAY.ARPA>
Cc: rrrs-authors@MC.LCS.MIT.EDU
Subject: define (resend) (long)
In-reply-to: Msg of 27 May 1986 13:20-EDT from Chris Haynes <cth%indiana.csnet at CSNET-RELAY.ARPA>
I'm afraid that we have a real disagreement here.
Much has been said about the pros and cons of the "MIT style" local define,
and it is clear that a consensus is not possible, so a compromise is in
order.
I disagree. Much has been said about MIT's INCREMENTAL DEFINE (which
T also has), but not much has been said at all about (static and local)
INTERNAL DEFINE, which is the only one which appears on the report.
This happened mostly for compatibility with S&ICP, not because the
people from MIT were trying to force it on anybody else (after all, we
cheerfully accepted LETREC, which we did not have before).
Using a different keyword, such as DEFINE-GLOBAL, to make global definitions
from lexically nested positions is not acceptible to us. We have tried to
live with such arrangements for some months now, and have found them
intolerable.
DEFINE-GLOBAL does not make sense for either T or MIT-Scheme. Neither
really has a global environment distinguished from the rest, thus
there is no environment where these definitions could be made. The
closest we (MIT) can come to this is making the definition occur in
the innermost environment created by means of MAKE-ENVIRONMENT (the
innermost locale in the case of T), but this seems arbitrary in our
case, to say the least, since all environments are created equal. In
T this is not the case, so this is a viable option. We would still do
it if everybody else agreed to it, but we'd rather not, since there
are other options (see below).
The idea is that it should be
possible, in any "standard" Scheme that supports some kind of macro package,
to get *either* style of lexical DEFINE by simply loading the appropriate
macro package.
What about Schemes that do not have macros at all? Does this mean
that they have to choose one of the two styles, and thus have no
possibility of running the "portable" code written using the other? I
disagree very strongly with having a feature with two possible
inconsistent semantics. The only option would be to remove its
optional status, and therefore remove it from the report completely.
Thus nobody would be able to use DEFINE at all in portable code.
Changing semantics now, besides being unacceptable to us, would mean
being purposely incompatible with S&ICP, and gratuitously incompatible
with the previous version of the report.
What is it that you do not like about DEFINE-GLOBAL? The name is too
long? Use DEFINE! or DEF instead. The first was suggested at the meeting
in Brandeis. Is the problem that it is not even in the report, so you
can't use it because it is not portable? I'm pretty convinced that we
(MIT) could be convinced of accepting it for the sake of consensus
after a little arm twisting (very little needed).
Note that there is a portable way of achieving the effect of
DEFINE-GLOBAL:
(define foo) ; or (define foo '*)
(define bar) ; or (define bar '*)
(let ((<local-state>))
(set! foo <whatever you want 1>))
(set! bar <whatever you want 2>)))
We often do this (although we have and use alternatives) to "export"
values to outer environments, but this gives us more control than
DEFINE-GLOBAL, since we can just place the DEFINEs in the environment
where we want the definitions to occur.
If you do not like the assignments, there is the following
alternative:
(with-exports (foo bar)
(let ((<local-state>))
(define-export foo <whatever you want 1>)
(define-export bar <whatever you want 2>)))
which would just be pretty syntax for the previous choice. Note that
DEFINE-EXPORT (or DEFINE!, or anything you want to call it) is nothing
special, since it trivially turns into SET!.
Note that the (FOO BAR) list could be made optional, meaning "trap"
all DEFINE-EXPORTs.
∂28-May-86 0827 @MC.LCS.MIT.EDU,@KATHERINE.THINK.COM:gls@AQUINAS.THINK.COM Remaining questions & remarks (1)
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Date: Wed, 28 May 86 10:43 EDT
From: Guy Steele <gls@Think.COM>
Subject: Remaining questions & remarks (1)
To: JAR@MIT-AI.ARPA
Cc: rrrs-authors@MIT-MC.ARPA
In-Reply-To: <"860527141917.1.jar@AI"@ROCKY-GRAZIANO.LCS.MIT.EDU>
Message-Id: <860528104332.1.GLS@KATHERINE.THINK.COM>
Date: Tue, 27 May 86 14:19 EDT
From: Jonathan A Rees <JAR@MIT-AI.ARPA>
...
There are at least sixteen different references to Common Lisp. I'm
going to try to remove some of them. We have to make it very clear that
Scheme is 11 years old and originated some of CL's ideas --- not the
other way around!
That's right! Good for you.
--Guy
∂28-May-86 0836 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA hash-consing
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Date: Wed 28 May 86 09:45:51-CDT
From: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: hash-consing
To: RRRS-Authors%mit-mc@CSNET-RELAY.ARPA
Cc: Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
Message-Id: <12210304495.60.BARTLEY@CSC60>
Has anyone had any experience with systems that use hashing CONS? I
remember the idea was in vogue 15 or 20 years ago as a way to lower
memory consumption, speed up EQUAL, and for theoretical (heretical?)
reasons. The idea is to use hashing techniques to make pairs that are
EQUAL? also be EQ?.
The disadvantages seem to be (1) slower CONS, (2) unclear semantics
for SET-CAR! and SET-CDR!, (3) separate spaces or tags (or something)
if both hashed and regular CONS exist, and (4) GC complications. Are
there any experimental results that demonstrate any significant
compensating advantages? If so, what are the circumstances?
The definition of CONS in the RRRRS guarantees that every pair
returned is unique, so hashing would seem to be out of the question.
However, I wonder if a HASH-CONS procedure has any merit.
Regards,
David Bartley
-------
∂28-May-86 1137 @MC.LCS.MIT.EDU:andy@aids-unix Re: define
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Date: Wed, 28 May 86 08:04:09 pdt
From: andy@aids-unix (Andy Cromarty)
To: JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU, cth%indiana.csnet@CSNET-RELAY.ARPA
Subject: Re: define
Cc: rrrs-authors@MC.LCS.MIT.EDU
If we are casting votes on DEFINE, I would observe that of the
half-dozen or so of us here who are directly involved in our Scheme
effort, only one of us favors any legitimate status for "global"
DEFINEs. (He happens to come from Indiana, BTW, and we may have
succeeded in changing even his mind on this issue.) The rest of us
have from the outset found Scheme-84's global DEFINE semantics to be
an abhorrent violation of the principles of lexical scope. In fact,
we assumed it was a compiler bug when we first ran across it.
Even where there is a most global environment, we are hard-pressed
to see what could justify advocacy of a special form that reaches
into it specially from an enclosed scope to destructively manipulate
its state. If we (collectively) need an extension of Scheme to achieve
this effect, let's promote binding environments to first-class objects and
define a destructor that treats them uniformly. (I believe, however,
that it is possible to write substantive, efficient, and above all,
elegant Scheme programs without the inclusion of such a destructor.)
I have always felt that the global DEFINE in Scheme-84 was a profound
design flaw that must be attributable to the unfortunate influence of
the Franz environment (both software and intellectual) in which Scheme-84
was constructed. I understand that there is a substantial difference of
opinion on this issue, but we find it difficult to see how global DEFINEs
are even arguably compatible with what we take to be fundamental design
principles of Scheme. In fact, as evidence of our objection to Scheme-84's
global DEFINE semantics, we have done some work on ripping this feature out
of a copy of the Scheme-84 compiler, replacing it with S&ICP's internal
DEFINE.
asc
p.s. My apologies for blitzing you with such a strong opinion; we hashed
this one out locally until it was beaten to death some time ago,
and our opinions have admittedly become somewhat calcified....
∂28-May-86 1241 @MC.LCS.MIT.EDU:dyb%indiana.csnet@CSNET-RELAY.ARPA Re: define (resend) (long) (short)
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Date: Wed, 28 May 86 13:30:30 est
From: Kent Dybvig <dyb%indiana.csnet@CSNET-RELAY.ARPA>
To: jinx@MC.LCS.MIT.EDU
Subject: Re: define (resend) (long) (short)
Cc: rrrs-authors@MC.LCS.MIT.EDU
It is too much to ask everyone who has learned to use "define" the
way we know and love it here to switch to either a new word or a
new meaning for internal definitions. We feel that we have given it
our best shot over the past year, having tried both "define!" and
"global-define". What it boils down to is that (1) the same name
should be used inside as out to define global variables and (2) the
right name is define.
You mentioned the possibility of omitting internal define altogether.
We would be satisfied with that. The report should say something to
the effect of portable code should only use the define/set! form (or
appropriate sugaring). This seems to be the only viable solution.
∂28-May-86 1736 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU define (resend) (long) (short)
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Date: 28 May 1986 20:34 EDT (Wed)
Message-ID: <JINX.12210411645.BABYL@MIT-OZ>
From: Bill Rozas <JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>
To: Kent Dybvig <dyb%indiana.csnet@CSNET-RELAY.ARPA>
Cc: rrrs-authors@MC.LCS.MIT.EDU
Subject: define (resend) (long) (short)
In-reply-to: Msg of 28 May 1986 14:30-EDT from Kent Dybvig <dyb%indiana.csnet at CSNET-RELAY.ARPA>
What it boils down to is that (1) the same name
should be used inside as out to define global variables and (2) the
right name is define.
Again, this does not make any sense in MIT Scheme, where user code
runs by default in an environment which inherits the "global"
bindings, rather than the one were the bindings actually exist. Top
level DEFINEs do not define in the global environment, but in whatever
environment the code is loaded. The default top level environment is
an environment with an empty top frame, and whose parent frame
contains the initial accessible bindings of the system. Our system
(local and incremental DEFINE) is perfectly consistent, since DEFINE
always acts on the environment where the definition is evaluated.
There is no difference between top level and inner environments. As a
matter of fact, top level is changed at various times, and thus top
level DEFINE acts on different environments at different times.
Indiana style DEFINE sounds horrendous to me because the evaluation
happens in one environment, while the "assignment" happens in another,
without making this explicitely visible. Nevertheless, I'm willing to
have it added it to the report as long as it has a different name
(DEF?). Note that if DEF is implemented, it will also "work" at top
level, so you can always use the same name.
You mentioned the possibility of omitting internal define altogether.
We would be satisfied with that. The report should say something to
the effect of portable code should only use the define/set! form (or
appropriate sugaring). This seems to be the only viable solution.
Again, this is being gratuitously different from the previous version
of the report, and S&ICP. We are keeping T and NIL, #!TRUE and
#!FALSE, just to be backwards compatible. Removing DEFINE would allow
implementations (like you) to have semantics completely incompatible
with the previous report.
Look guys, I hate BEGIN with all my guts. I am not fighting against
it. We had a vote at Brandeis and it WON (I cast the only vote
against it). I (and JAR, and GJS, who hate it almost as much as I do)
abide by that decision (although I occasionally grumble about it, as
well as about REC). I would very much like to see it out, but if
everybody does this we will never agree on anything, because everybody
will find something they do not like. I'm afraid that DEFINE must
stay the way it is, and I (and the rest of the Scheme people at MIT,
plus others, I'm sure) will oppose any changes to it. You are
reopening a can of worms which was closed at Brandeis. Since we are
at it, why don't we argue again about when CALL-WITH-INPUT-FILE closes
the file or whether the name should be LETREC or LABELS?
∂28-May-86 2216 @MC.LCS.MIT.EDU:gls@Think.COM Embedded DEFINE forms
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Date: Thu, 29 May 86 01:14:45 edt
From: gls@Think.COM (Guy Steele)
Message-Id: <8605290514.AA08588@Godot.Think.COM>
To: rrrs-authors@mc
Subject: Embedded DEFINE forms
I have watched the controversy going on for quite some
time, and it seems to me that at this late date, on the
eve, apparently, of widespread publication of a standard
for SCHEME, that there is not consensus in the SCHEME
community on the subject of embedded DEFINE forms.
If the community cannot agree, nor even agree to agree
on some arbitrary choice, then the matter should not be
standardized.
I see no harm in the standard not defining what happens to
embedded DEFINE forms. This would allow the various camps
to be upward-compatible extensions of the standard (though
of course not with each other in this regard). RRRS might
even have, as a footnote or appendix, descriptions of the
competing proposals.
--Guy
∂28-May-86 2243 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: Notes about (↑ revised 3) report
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To: KMP@SCRC-STONY-BROOK.ARPA
Cc: JAR@MC.LCS.MIT.EDU, RRRS-AUTHORS@MC.LCS.MIT.EDU,
willc%tekchips.tektronix.csnet@CSNET-RELAY.ARPA
Subject: Re: Notes about (↑ revised 3) report
In-Reply-To: Your message of Thu, 22 May 86 18:53 EDT.
<860522185327.2.KMP@RIO-DE-JANEIRO.SCRC.Symbolics.COM>
Date: 27 May 86 13:07:52 PDT (Tue)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
Here are the answers I prefer to KMP's starred questions; words within
brackets were edited by me.
* Does the [port] become closed as a side-effect of hitting eof?
No.
* Is it an error to read from a closed [port], or does [an eof-object]
just keep getting returned?
It is an error.
* Can you read the eof object twice at the end of a file using READ ?
How about if using READ-CHAR ? PEEK-CHAR ?
Yes. Yes. Yes.
* Is it possible to detect whether a [port] is closed?
Impossible using only the procedures documented in R↑3RS. I'd like the
language to remain silent on whether a closed port is still a port.
* Is it acceptable for close on certain [ports] to not really close the
[port]? For example, I could imagine implementing terminal [ports] or
[ports] into editor buffers in a way such that they just always claimed
to be open and close was a no-op.
Yes.
KMP:
Also on p30, it seems to me that the notion of CHAR-READY? is not a
useful one. It's subject to timing errors in multi-processed systems
and/or systems which allow asynchronous interrupts. The Lisp Machine's
TYI-NO-HANG paradigm is much better, since it has a more test-and-set
feel to it and is more easy to use reliably. I suggest that CHAR-READY?
should be flushed and replaced by a READ-CHAR? which returns either a
character if one is ready, or NIL otherwise. This gets you out of the
bind with rubbing out stuff that CHAR-READY? has noticed, which is really
an awful crock. I believe that TYI-NO-HANG will interact satisfactorily
with Lispm-style rubout handlers.
To some extent I agree with this, but I don't think READ-CHAR? by itself
is any better for multi-processing than CHAR-READY?.
Peace, Will
∂29-May-86 1417 NET-ORIGIN@MC.LCS.MIT.EDU define
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Date: Thu, 29 May 86 16:13 EDT
From: Jonathan A Rees <JAR@MIT-AI.ARPA>
Subject: define
To: cth%indiana.csnet@CSNET-RELAY.ARPA, rrrs-authors@MIT-MC.ARPA
In-Reply-To: The message of 27 May 86 13:20-EDT from Chris Haynes <cth%indiana.csnet@CSNET-RELAY.ARPA>
Message-ID: <"860529161305.5.jar@AI"@ROCKY-GRAZIANO.LCS.MIT.EDU>
I didn't want to make any changes to the report as fundamental as this.
A change to DEFINE also seems infeasible given how constroversial the
topic is and always has been. I am trying to sidestep controversies
right now, so that I can get something done. Maybe in next year's
revision (??) we can address this question.
As we agreed at Brandeis, few of us wholeheartedly like internal
definitions, but they should be described ("nonessentially") because
S&ICP uses them. This was a difficult compromise for us to arrive at,
and I think it would be much too painful at this point to retract it.
And now we have another reason to leave them in, which is compatibility
with the RRRS.
T originally had the semantics that you prefer for DEFINE (although
definitions aren't "globally" effective, they're scoped to the innermost
lexical contour which is willing to accept it). Many users found it to
be a very nice feature, for the same reasons you do. However, I have
recommended to the current T implementors that they remove the feature,
for several reasons:
(a) It makes it more difficult for humans & programs to scan a file
to find its definitions.
(b) It's not always obvious which environment it is intended the
definitions go in; like MIT Scheme, T has no notion of "top level."
(c) It really confuses anyone who has ever seen S&ICP or MIT Scheme.
The old meaning will be retained in T, probably under some other name
(or anonymously, since T has anonymous special form types). Kent and
others still stand by the old meaning.
Here is how I think I would put the functionality that "global define"
provides into a language like Scheme. (A better language than Scheme
might do it better.) Invent a special form (or macro) called something
like EXPORT or PROVIDE or MODULE which works as follows:
(provide <var1> <var2> ...)
is equivalent to
(lambda (<temp>)
(case <temp>
((<var1>) <var1>)
((<var2>) <var2>)
...
(else <error>)))
where <temp> is a variable different from <var1>, <var2>, ....
Then instead of
(let ((state ...))
(define-global reader ...)
(define-global writer ...)
...)
you can write
(define i/o-system
(letrec ((state ...)
(reader ...)
(writer ...)
...)
(provide reader writer ...)))
(define reader (i/o-system 'reader))
(define writer (i/o-system 'writer))
...
The PROVIDE special form would be useful for many other applications as
well (e.g. object-oriented programming).
If this is too verbose for you, I think other kinds of macros could
almost as easily be designed which like the above raise no new semantic
questions.
- Jonathan
∂29-May-86 1438 NET-ORIGIN@MC.LCS.MIT.EDU schedule
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Date: Thu, 29 May 86 14:36 EDT
From: Jonathan A Rees <JAR@MIT-AI.ARPA>
Subject: schedule
To: rrrs-authors@MIT-MC.ARPA
Message-ID: <"860529143648.3.jar@AI"@ROCKY-GRAZIANO.LCS.MIT.EDU>
Thanks to everyone who has read the draft report so carefully. But
don't stop -- keep those cards and letters coming. I called Wexelblat
about the production schedule for August and September SIGPLAN. He said
he has to have it in his hands by June 13 (needs a page count sooner) if
it's to go into the August issue (which gets mailed out the first week
of August). So this gives us a little more time. However: the August
issue is getting to be pretty full; if we think it's urgent that it be
published, it's possible to get it in, but he would prefer if it waited
for the September issue. I told him that some of the coauthors were
ancy to get the thing published and that I'd ask them what they thought.
Note that it won't get out to people before the Lisp conference in any
case.
I'm inclined to try to push and get it into the August issue, but if
people think we should spend more time arguing about things (I had no
idea so much controversy would arise at this late date), then we can
wait.
Jonathan
∂29-May-86 1450 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA define
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Date: Thu 29 May 86 10:35:51-CDT
From: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: define
To: RRRS-Authors%mit-mc@CSNET-RELAY.ARPA
Cc: Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
Message-Id: <12210575742.48.BARTLEY@CSC60>
There is clearly no chance of a consensus on the meaning of an
internal DEFINE. It seems fair to let the current draft go through
without changes from the previous one, since that was the
understanding at Brandeis.
The only viable solutions for the future are to remove internal
DEFINEs entirely (as Guy suggests) or to persuade the Indiana folk to
choose a new name. (I thought `DEFINE!' was appropriate--whatever
happened to it?)
I prefer the second option. Now that Scheme systems are being broadly
distributed, it is important for us to show a united front. I would
understand a user's anger if he could not find compatible
implementations for his range of machines.
I understand IU's feelings, but I think a compromise with DEFINE! or
DEF or whatever is in the same spirit as all of us have solved similar
inconsistencies in the past.
Regards,
David Bartley
-------
∂29-May-86 1454 @MC.LCS.MIT.EDU:WAND%northeastern.edu@CSNET-RELAY.ARPA R3RS draft -- procedural
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Date: Thu, 29 May 86 10:32 EST
From: MITCHELL WAND <WAND%northeastern.edu@CSNET-RELAY.ARPA>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: R3RS draft -- procedural
I have been looking at the draft of the R3RS which was distributed (dated 22
May). There are certainly a number of issues (some serious) which need to be
resolved. In addition, there are many places in the report (marked by open
brackets) which have not yet been filled in, and where the completion is
substantive, rather than presentational.
In view of this situation, I think it would be a serious mistake to "mail it
to SIGPLAN June 1 come hell or high water". I think those of us whose names
will appear as authors of the report deserve to see a CLEAN draft before it is
submitted. The document is too important not to get it right.
I will send out my other comments in some other messages.
Mitch Wand
∂29-May-86 1545 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU R3RS draft -- procedural
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Date: Thu, 29 May 86 18:42:02 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: R3RS draft -- procedural
To: WAND%northeastern.edu@CSNET-RELAY.ARPA
cc: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Thu 29 May 86 10:32 EST from MITCHELL WAND <WAND%northeastern.edu at CSNET-RELAY.ARPA>
Message-ID: <[AI.AI.MIT.EDU].48143.860529.JAR>
Date: Thu, 29 May 86 10:32 EST
From: MITCHELL WAND <WAND%northeastern.edu at CSNET-RELAY.ARPA>
In view of this situation, I think it would be a serious mistake to "mail it
to SIGPLAN June 1 come hell or high water". I think those of us whose names
will appear as authors of the report deserve to see a CLEAN draft before it is
submitted. The document is too important not to get it right.
OK.
∂29-May-86 1610 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA response to new draft report (long)
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Date: Thu 29 May 86 10:19:27-CDT
From: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: response to new draft report (long)
To: RRRS-Authors%mit-mc@CSNET-RELAY.ARPA
Cc: Bartley%ti-csl.csnet@CSNET-RELAY.ARPA, JAR%ai.ai.mit.edu@CSNET-RELAY.ARPA
Message-Id: <12210572757.48.BARTLEY@CSC60>
Here are my (hasty) comments on the new draft Report.
COMMENTS ON THE TEXT OF THE DOCUMENT:
[page 1]
My name is "David Bartley", but "D.H.Bartley" is better than "D.Bartley".
Why use zero-origin indexing for section numbers?
[page 2]
Use italics and capitalization for consistency in "revised report
[29]" in 2nd paragraph of Background.
The term "coalescing" in the 2nd-to-last paragraph is not defined
anywhere.
[page 4]
Remove "will" from "Italicized names will stand for..."
Pluralize "argument" in "the append procedure is being passed zero or
more list argument."
Add "be" in "this report explicitly does not specify what value should
[be] returned." at end of 0.2.2.
Change "Upper and lower case letters are never distinguished..." in 1
to something like "Upper and lower case forms of a letter are never
distinguished...". Surely `A' is distinct from `b'.
Are #t and #f considered identifiers?
[page 5]
In 1st paragraph of 1.1: "Whitespace may occur..., but not within a
token." Is a string containing a space a token? The character `#\ '?
Typo: change `occuring' to `occurring'.
The statement "Backslash isn't used by Scheme except within string
constants" is awkward and negative.
Remove "are not used in Scheme right now but" from "... curly braces
are not used in Scheme right now but are reserved...".
Change "Like Algol or Pascal" to "Like Algol and Pascal".
[page 6]
In 2.1, the words "most values count as true, but a few--notably #f--
count as false" should be tightened up, since section 5.0 on page 13
makes it clear that only #f and the empty list count as false IN
CONDITIONAL EXPRESSIONS. (Is "in conditional expressions" a
qualifier???)
[page 7]
Fix "see section refdefine" in 3.0.2.
Is 3.0.2 a good place to take note that () is not a good procedure call?
What is meant by "here we will ASSUME that <body> is simply a sequence
of one or more expressions" in 3.0.3?
[page 8]
Please change the descriptions of COND and CASE to be what they were
in the RRRS (modulo the small changes we seem to have consensus on).
I see no reason to get carried away with describing the permissible
types for <datum> in a CASE key list. Just define CASE as using MEMV
(or EQV?) and let the implications hang out!
[page 10]
The first LET* example at the top left of the page is confusing, since
the first <binding> is decomposed into <variable> and <init> and the
others are not.
At the bottom of the first column, change the second instances of
<variable1> and <init1> to have subscript 2.
The words "... are variables which do not occur in the original LETREC
expression..." are confusing. Would a new binding of the identifier
(or is it variable) <temp1> be an occurrence of <temp1>? Similar
wording appears elsewhere in the document (e.g. with DO).
[page 11]
Specify that <name> in named LET must be an identifier (or is it
"variable").
[page 12]
Section 3.1.4: The wording "(for example, by a call to the FORCE
procedure)" begs for elaboration. I think it makes sense to postpone
most of the discussion to page 27ff, as JAR does, so let's use a
"white lie" here and mention only FORCE as a way to collect on a
promise. All other ways are extensions.
[page 13]
Change the last line of 4.1.0 from "Global definitions are essential;
all Scheme implementations must support them." to something like "This
semantics for top level definitions is essential." What does "global
definition" mean? The clause after the ";" is redundant.
I feel uncomfortable about using the term "lambda body" to include the
"body" of a LET or DEFINE expression, as is done in 4.2.
Why not retitle section 5 to be something like "Standard Procedures"
instead of "Initial Environment"? The text makes it clear that these
procedures are the standard bindings of variables in the initial
environment, so it doesn't have to be emphasized in the title. A
person looking at the table of contents on page 1 is likely to be
confused.
[page 14]
How about adding (EQ? NIL 'NIL) ==> #F as another example at the end
of 5.0 to hammer the point home?
Add "in the same order" at the end of "Two procedures are
operationally equivalent iff ... they return the same value and
perform the same side-effects." (Or is that implied by `having the
same side-effects'?)
The wording "it will always err on the conservative side" seems to say
that EQV? tries to do the "right" "wrong thing"!
[page 15]
Change "Objects of distinct types WILL NEVER BE operationally
equivalent, BUT FALSE and the empty list are permitted to be
identical..."
to "Objects of distinct types ARE NEVER operationally equivalent,
EXCEPT THAT #F and the empty list are permitted to be
identical...".
The second sentence of the description of EQUAL? should say that EQV?
is used for all objects except pairs, vectors, and strings.
[page 16]
Change "same" to "equivalent" in the comparison of (a b c d e) and its
dotted form.
[page 17]
APPEND! always side-effects all but its last argument.
[page 18]
Change "(in the sense of EQV? and EQ?)" to "(in the sense of EQ?)" or
"(in the sense of EQV?)". (Why mention both?)
What is meant by "returned" in the second and third sentences of the
description of SYMBOL->STRING? How about "created"?
[page 19]
The previous Report used all caps for the words NUMBER, COMPLEX, ...,
for EXACT and INEXACT, and [page 23ff] INT, RAT, FIX, FLO, ... . I
think that is less confusing than using the same typeface used for
Scheme identifiers.
[page 20]
Change the title of 5.4.2 from "Syntax" to something like "Number syntax".
Rephrase "to make all user populations happy". >I'm< not happy with
having both forms (e.g., both = and =?) and I'd settle for EITHER ONE!
[page 25]
JAR has omitted an important paragraph in the previous Report's
discussion of strings. The sixth paragraph on page 51 of the RRRS,
beginning "In phrases such as...", clarified in one place how
substring START and END work. The descriptions of SUBSTRING (etc)
don't make this clear at all.
[page 26]
If we only have SUBSTRING-MOVE-RIGHT! to support text editors, let's
flush it! This is only the tip of the iceberg when it comes to handy
little utility functions for building editors.
[page 27]
The dual use of VECTOR in the example starting (LET ((VECTOR (VECTOR...
is confusing.
For consistency, change ELTS in LIST->VECTOR to LIST.
[page 28]
Change "they" to "to" in "but they illustrate the property that the
value of a promise is computed at most once."
The second "bullet" at the top of the second column is not an
extension but an implementation issue (I think).
[page 29]
Restore the mention of the alternate name CALL/CC at the end of the
rationale for CALL-WITH-CURRENT-CONTINUATION.
[page 39ff]
Add index entries for `identifier' and `variable'.
------------------------------------------------
[Following are my responses to JAR's specific questions on language and
presentation. His question is left adjusted, my response is preceded
by ` ******* '.] I've omitted some questions/proposals I agree with
or have no comment on.
Questions on LANGUAGE
I left CASE as is, using EQV? as the comparison, and I explicitly stated
that the object ought to be boolean, character, number, or symbol. But
shouldn't it allow empty lists, vectors, and strings, too?
******* Define it in terms of EQV? and define (EQV? '() '()) ==> #T.
******* This is consistent with Common Lisp's CASE, which uses EQL.
May structure be shared in cases like (APPEND '(A B) '()) , or should APPEND
be Common Lisp compatible? [Bartley says sharing would be a gratuitous
incompatibility with CL, I'm invlined to agree.]
******* Don't share structure with any argument but the last.
Should APPEND and APPEND! explicitly allow any object as last argument
(CL compatible)?
******* Yes.
Should APPEND! disallow () as other than last argument?
******* No.
Can we specify that DISPLAY of a character does the same thing as
WRITE-CHAR?
******* Yes.
What should be said, if anything, about the desirability and/or legality
of EQUAL? failing to terminate? Rozas thinks an implementation with
this property is in error.
******* Leave it as it is. It is `an error' not to terminate.
In light of the vagaries of CALL-WITH-xxPUT-FILE, perhaps it
would be a good idea to explicitly state that closing a closed port
should be a no-op instead of an error.
******* Yes.
-----
Questions on PRESENTATION
Should the various examples which use DEFINE be changed to use the
(define (foo ...) ...) syntax instead of (define foo (lambda ...))?
Several people have told me that all those LAMBDA's could unnecessarily
intimidate SIGPLAN readers.
******* LAMBDA is what it's all about; but I don't really care.
There are two places (in descriptions of let* and letrec) where it is
necessary to create a lambda body in a context (such as the tail of a
BEGIN) where there isn't one already. What is the cleanest way to do
this? Is (let () ...) ok, or would ((lambda () ...)) or something else
be better?
******* Use (LET () ...).
Should the complete presentation of FORCE appear up front with DELAY, or
delayed until the place where the entry for FORCE appears?
******* It's OK where it is, but see my comments above.
-----
Notes on LANGUAGE
The selectors in a CASE expression must be distinct.
******* OK.
I have left CASE and COND syntax as in RRRS: there must be at least one
clause, but it may be an ELSE clause.
******* Yes--I don't like the rewrite in the new draft.
BOOLEAN? is essential.
******* I suppose so.
No agreement on COND or BEGIN. I have left them as in RRRS.
[To do: fix the BNF to agree!]
******* Yes, but keep `test' instead of `guard'.
The RRRS explicitly allows internal definitions in the body of a LETREC.
They are scoped to the body only, not to the entire expression. I can
flush this "feature" if a movement arises to do so; it seems sufficient
to me to permit only expressions (not definitions) in the body.
******* Allow them.
The list to which the rest argument gets bound must be newly allocated.
******* Yes. Common Lisp screwed this up.
There was strong sentiment both for removing REC and for removing
NAMED-LAMBDA. However, the sentiment was not unanimous. I don't
understand why it should have matterred so much, since neither is an
essential feature. If these are present, shouldn't everyone's favorite
features be present too? ... Supporters of REC included Kent Dybvig and
Dan Friedman. Supporters of NAMED-LAMBDA included Jim Miller and Henry
Wu. In addition, Bill Rozas insisted that if REC stayed, then
NAMED-LAMBDA must stay too, but he was willing to see both go.
******* Keep them both.
APPEND! necessarily clobbers its arguments (other than the last and
empty ones).
******* Yes. It's meaningless otherwise.
Many people wanted the number predicates pruned (i.e. choose between <
and <?). No agreement here, so both stay.
******* I still can't understand why we can't get agreement, but
******* having both forms is OK until we do. I'll live with either form.
The case sensitivity issue was a very sensitive one (so to speak). I
did not change the report's stance of symbol case insensitivity.
******* Let's remain case-insensitive.
-----
Notes on PRESENTATION
******* I agree with (or don't care about) the rest of the issues.
-------------------------------------------------
BTW, I generally agree with Will's answers to KMP's questions.
Regards,
David Bartley
-------
∂29-May-86 1610 @MC.LCS.MIT.EDU,@CSNET-RELAY.ARPA,@boethius.think.com:gls@AQUINAS.THINK.COM hash-consing
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Date: Thu, 29 May 86 16:50 EDT
From: Guy Steele <gls@GODOT.THINK.COM>
Subject: hash-consing
To: Bartley%ti-csl.csnet@CSNET-RELAY.ARPA,
RRRS-Authors%mit-mc@CSNET-RELAY.ARPA
Cc: gls@AQUINAS.THINK.COM
In-Reply-To: <12210304495.60.BARTLEY@CSC60>
Message-Id: <860529165056.1.GLS@BOETHIUS.THINK.COM>
Dr. Eiichi Goto has done the greatest amount of work on hash-consing;
I think he may have invented the idea. See the bibliography of the
paper by Goto et al. in the 1982 Lisp conference.
--Guy
∂29-May-86 1706 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: global definitions
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To: rrrs-authors@MC.LCS.MIT.EDU
Cc: willc%tekchips.tektronix.csnet@CSNET-RELAY.ARPA
Subject: Re: global definitions
Date: 29 May 86 15:29:02 PDT (Thu)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
Though I spent time in Indiana, I must join with JINX and Andy in
protest against the very idea of global definitions. If we must
have global definitions, I propose that the syntax be
(SETF (SYMBOL-FUNCTION 'FOO) ...)
so as to avoid gratuitous differences between Scheme and Common Lisp.
As prelude to more serious comments, let me summarize the status quo:
INCREMENTAL DEFINE: Not in the report, but appears in S&ICP. Supported
only by MIT Scheme, though T has something similar.
INTERNAL DEFINE: Optional in the report, pervasive in S&ICP. Alternative
syntax for LETREC. Supported by MIT Scheme, PC Scheme, and MacScheme.
TOP-LEVEL DEFINE: Essential in the report. It is up to the programming
environment whether top-level definitions are implemented as global
bindings, incremental bindings, or assignments; it makes very little
semantic difference. Supported by everyone.
I don't want to give in to Guy's suggestion that internal definitions be
dropped entirely because it would return us to the days when we couldn't
read each other's code. The implementations that support internal
definitions for compatibility with S&ICP would go on supporting them,
while people using Chez Scheme and Scheme-84 would write syntactically
identical code that does something completely different. If everyone
could agree not to use DEFINE except at top level I might agree with Guy,
but that just isn't going to happen. (For instance, the idea of dropping
internal DEFINE wouldn't even have come up if the people at Indiana
weren't so insistent on using the word DEFINE at places other than top
level.)
Though I once programmed in the Indiana style, I have found it easy to
switch to the new idiom:
(define foo)
(define bar)
(let (<local state>)
(set! foo ...)
(set! bar ...))
I am partly in the dark because I have not yet received Chris Haynes's
message, but I suspect that folks at Indiana have not really given the
above idiom a chance because the one message I have received says only
that both "define!" and "global-define" were tried.
In short, I'm not a fan of the internal definition syntax, but I vote in
favor of keeping it in the report so as to prevent the syntax from being
used with two incompatible semantics.
Peace, Will
∂30-May-86 1432 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA definitions; APPEND!; etc
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To: rrrs-authors@MC.LCS.MIT.EDU
Cc: jar@MC.LCS.MIT.EDU
Subject: definitions; APPEND!; etc
Date: 30 May 86 12:08:29 PDT (Fri)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
Since the report won't appear in SIGPLAN Notices until after the Lisp
conference, I too favor waiting another month.
----------------------------------------------------------------
At Brandeis we agreed that (BEGIN (DEFINE ...) (DEFINE ...)) would be
flattened when it appeared at the beginning of a lambda body, but I
forgot to mention that in the RRRS. It seems simplest to extend that
flattening to apply to the top level as well by changing the formal
syntax of <definition> to be
<definition> --> (define <variable> <expression>)
| (define (<pattern> <formalz>) <body>)
| (begin <definition>+)
This still rules out things like
(begin (define up)
(define down)
(let ((n 0))
(set! up (lambda () (set! n (1+ n)) n))
(set! down (lambda () (set! n (-1+ n)) n))))
After writing the new syntax for <program> that would be needed
to allow this, I decided it isn't worth it.
----------------------------------------------------------------
I prefer dropping both NAMED-LAMBDA and REC to leaving them both
in.
----------------------------------------------------------------
I have a few remarks to add to some of David Bartley's comments.
>Add "in the same order" at the end of "Two procedures are
>operationally equivalent iff ... they return the same value and
>perform the same side-effects." (Or is that implied by `having the
>same side-effects'?)
There is still considerable research directed toward formulating
a satisfactory notion of operational equivalence for procedures
with side effects in the presence of concurrency, or even in the
presence of asynchronous interrupts. To see that the definition
on page 14 is inadequate, consider that
(lambda (x) (set! x (1+ (1+ x))) x)
and
(lambda (x) (set! x (1+ x)) (set! x (1+ x)) x)
are operationally equivalent but
(lambda (y) (set! x (1+ (1+ y))) x)
and
(lambda (y) (set! x (1+ y)) (set! x (1+ x)) x)
are not.
>APPEND! always side-effects all but its last argument.
No, APPEND! should not be required to perform side effects. This is not
as silly as it may sound. In an implementation using the Hewitt-Lieberman
gc algorithm, for example, side effects to sufficiently old structures are
likely to be more expensive than consing. APPEND! should be free to decide
for itself which technique is fastest.
I would feel differently if APPEND! returned an unspecified value, as
does VECTOR-SET!.
>Rephrase "to make all user populations happy". >I'm< not happy with
>having both forms (e.g., both = and =?) and I'd settle for EITHER ONE!
I have been one of the main holdouts here, but I too am now willing to
settle for either one.
>If we only have SUBSTRING-MOVE-RIGHT! to support text editors, let's
>flush it! This is only the tip of the iceberg when it comes to handy
>little utility functions for building editors.
I agree. I think we should write other documents, however, to describe
the portable Scheme libraries that people have written, and we should
work on improving portability and availability.
peace, Will
∂30-May-86 1650 @MC.LCS.MIT.EDU:OXLEY%ti-csl.csnet@CSNET-RELAY.ARPA Re: Embedded DEFINE forms
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Date: Fri 30 May 86 17:42:25-CDT
From: Don Oxley <OXLEY%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: Re: Embedded DEFINE forms
To: gls%Think.COM@CSNET-RELAY.ARPA, rrrs-authors%mc@CSNET-RELAY.ARPA
In-Reply-To: <8605290514.AA08588@Godot.Think.COM>
Message-Id: <12210915540.62.OXLEY@CSC60>
I have generally avoided getting into these discussions as David has
represented our viewpoints very effectively. However, I am becoming
concerned about what looks like a potentially destructive argument over
DEFINE.
It seems to me that it is unlikely that very many users outside of the
aficionados at MIT and IU are likely to use embedded DEFINE at all -
except as they may have seen it in S&ICP. I would hate to see
"outsiders" back away from using SCHEME because they see a religious war
going on within the community.
My first suggestion is to leave it as we decided at Brandeis - based on
the notion that we had agreement (even if grudging) and we do not have
an agreement on a change. Possibly better is Guy's suggestion to
leave it undefined (which I think is roughly equivalent to letting the
dominant dialect win).
I would be very hesitant for us to have to change PC Scheme in an
incompatible direction. I'll hazard a guess that PCS is or is close to
becoming the most widely used Scheme today, so we are trying to be
somewhat careful about compatibility (although as I said, I doubt if
this will affect very many users). Either leaving the position as it is
or making it undefined would leave PCS alone.
Please, let's not let this become a divisive issue that hurts the spread
of Scheme to those who don't care about so technical an issue and
merely what to know what the langauge does and does not do.
--Don
-------
∂30-May-86 1703 @MC.LCS.MIT.EDU:WAND%northeastern.edu@CSNET-RELAY.ARPA procedure (Tnx)
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Date: Fri, 30 May 86 10:04 EST
From: MITCHELL WAND <WAND%northeastern.edu@CSNET-RELAY.ARPA>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: procedure (Tnx)
Thanks to Jonathan for so promptly accepting my suggestion that we delay
publication until these issues are resolved.
-- Mitch
∂30-May-86 1703 @MC.LCS.MIT.EDU:WAND%northeastern.edu@CSNET-RELAY.ARPA define -- a modest proposal
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From: MITCHELL WAND <WAND%northeastern.edu@CSNET-RELAY.ARPA>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: define -- a modest proposal
I think it is clear that we do not have a consensus on the semantics of
internal DEFINE. My understanding of the compromise reached at Brandeis was
that lexically nested DEFINE would retain the MIT semantics, whereas
the IU semantics could be obtained by using DEFINE! . The current report
does not appear to be compatible with that compromise, because it would appear
necessary to do a
(define foo 'hunoz)
at top-level before one can legally do a set! on foo from an interior scope.
Analyzing this situation, there are two operations involved in a define:
1. Binding the identifier to some location.
2. Storing a value in that location.
The latter operation is clearly doable by set!, so the only issue is #1.
The MIT semantics has DEFINE performing #1 on the current scope. The
advantage of this proposal is that it is uniform on both "top-level" and
interior scopes. The disadvantage is that it essentially creates a new scope
(region) in the program which is not delimited by parentheses. [Perhaps the
grammar could be fixed to recognize this new, non-list-structure phrase?].
This is an unpleasantness at the top level which I do not think we understand.
[Perhaps we should separate DEFINE into two procedures:
(make-local-variable 'foo)
(set! foo value)
[shades of GNU Emacs-Lisp!!]]
[Another, separate, argument against including internal define as an optional
feature in the report is that, unlike the other optional features in the
report, it requires pervasive modifications in many other sections of the
report].
Nevertheless, I am not yet arguing for elimination of internal defines from
the report, in keeping with the compromise reached at Brandeis.
What I will argue for is the following:
An implementation may have a top level (initial, whatever) environment in
which every possible identifier is bound (though only some are initialized).
This would allow programs in that implementation to do a set! on a global
variable (excuse me, a variable in the current top-level environment) from an
internal scope without having to explicitly bind the variable in the initial
scope. It would also allow MIT-style define to proceed, as it does not
require the existence of a distinguished global environment.
I think this proposal retains the spirit of the Brandeis agreement on this
issue.
Mitchell Wand
∂31-May-86 0108 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU define -- a modest proposal
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Date: 31 May 1986 00:32 EDT (Sat)
Message-ID: <JINX.12210979336.BABYL@MIT-OZ>
From: Bill Rozas <JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>
To: MITCHELL WAND <WAND%northeastern.edu@CSNET-RELAY.ARPA>
Cc: rrrs-authors@MC.LCS.MIT.EDU
Subject: define -- a modest proposal
In-reply-to: Msg of 30 May 1986 11:40-EDT from MITCHELL WAND <WAND%northeastern.edu at CSNET-RELAY.ARPA>
I may have misunderstood your message, but I'm afraid you are still
confusing (local static) INTERNAL DEFINE with (dynamic, horrible
semantically) INCREMENTAL DEFINE. They have nothing in common (except
sharing the keyword).
INTERNAL DEFINE does NOT create a new scope. The scope is created by
the surrounding LAMBDA, LET, or LETREC expression, and is therefore
bounded by parentheses.
(let ()
(define foo ...)
(define bar ...)
<some expression>)
should be exactly equivalent to
(letrec ((foo ...)
(bar ...))
<some expression>)
As a matter of fact, I originally implemented LETREC in MIT-Scheme
(and it is still implemented in this way in MIT CScheme, I believe),
by transforming the second expression into the first.
Thus, the (INTERNAL) DEFINEs do not establish the context. The
context is established by LET.
Your proposal of separating DEFINE into
(make-local-variable 'foo)
(set! foo value)
seems to violate this semantics. It appears to be advocating for
INCREMENTAL DEFINE, which is NOWHERE on the report. Indeed, MIT
Scheme has a primitive procedure which implements INCREMENTAL DEFINE,
on top of which MAKE-LOCAL-VARIABLE could be implemented trivially,
but we are certainly not advocating for a feature we don't feel
comfortable with ourselves.
INTERNAL DEFINE is purely declarative, it does not involve ANY side
effects. INCREMENTAL DEFINE, on the other hand, is mostly imperative,
and involves side effecting environments.
As far as I know (please correct me on this), INTERNAL DEFINE has no
semantic problems, its only problem is purely syntactic: it makes the
evaluator (compiler, syntaxer, code walker, whatever) harder to write
since it has to collect all the definitions which occur in a scope
before processing the expressions. Since the report only allows
definitions as the very first thing in a block (it's the only place
where they make sense), collecting them is trivial.
∂31-May-86 0331 NET-ORIGIN@MC.LCS.MIT.EDU wanted: teaching do's and dont's
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Date: Mon, 23 Dec 85 14:41:29 est
From: Edward Sciore <sciore%bostonu.csnet@CSNET-RELAY.ARPA>
To: SCHEME@mit-mc.ARPA
Subject: wanted: teaching do's and dont's
I will be teaching from the "Structure and Interpretation..." book
spring semester. Students will be sophmores/juniors with at least 2
semesters of Pascal behind them. Does anybody know of things that I
should be wary of? How fast should I go in order to get through chapter
4? Will their previous programming experience allow the students to
handle the material more easily? Any tips people have discovered
will be appreciated. Thanks.
Ed Sciore
Boston University CS Dept
sciore@bostonu.CSNET
∂31-May-86 0539 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU wanted: teaching do's and dont's
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Date: 31 May 1986 08:33 EDT (Sat)
Message-ID: <JINX.12211066871.BABYL@MIT-OZ>
From: Bill Rozas <JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>
To: Edward Sciore <sciore%bostonu.csnet@CSNET-RELAY.ARPA>
Cc: SCHEME@MC.LCS.MIT.EDU
Subject: wanted: teaching do's and dont's
In-reply-to: Msg of 23 Dec 1985 14:41-EST from Edward Sciore <sciore%bostonu.csnet at CSNET-RELAY.ARPA>
Our experience at MIT is that it is often the case that students with
previous programming experience suffer MORE in the course than
students without such experience, since the latter are not biased.
In particular, students familiar with BASIC and FORTRAN (and probably
PASCAL) tend to have a hard time adapting to the functional style
encouraged by Scheme. They view DEFINE as assignment, which it isn't,
and even if they get used to the functional style, when assignment
(SET!) is finally introduced, they often revert to the ugly imperative
style. They sometimes have this crazy notion that imperative style is
more efficient. Interestingly enough, code with side effects is often
LESS efficient in T and in MIT Scheme with the new compiler.
Although Pascal is, like Scheme, lexically scoped, students do not
have a really hard time accepting this, so I'm not sure it's a real
advantage.
Obvious potential stumbling blocks, beyond style:
Absence of VAR parameters, used sometimes to "return" multiple values in
Pascal. This is usually done in Scheme (in dialects without multiple
values) in one of two ways: returning a data structure (list or
vector) with the appropriate contents, or passing an explicit
continuation with many parameters to the procedure that wants to
return multiple values, which will, instead of returning, invoke its
explicit continuation with the multiple "returned" values.
Absence of iteration constructs. Standard Scheme has DO, but it is
not used in S&ICP, in fact, we did not even have it in MIT Scheme
until the report describing Standard Scheme came about. Iteration has
to be achieved through syntactic recursion. One of the reasons for
not having syntactic sugar in MIT Scheme (originally) was to emphasize
this point, and force students to deal with the issue.
Absence of explicit allocation. Memory management in Scheme is
automatic, rather than manual.
Eventually, the fact that thanks to tail recursion and first class
procedures (and worse, cwcc, but this is not covered in S&ICP), Scheme
is a completely unstructured language (in the sense of "structured
programming"). Procedures (lambda expressions) are labels, and
application is GOTO, and any arbitrary control structure can be built
on top of this.
PS: There is a teacher's manual for S&ICP written by Juile Sussman.
It is very good. It contains more examples, more problems, and a very
detailed description of where students go wrong in various places, and
what points need further emphasis. I believe (HAL or GJS can correct
me here) that it can be obtained through McGraw Hill.
∂31-May-86 0738 @MC.LCS.MIT.EDU:dyb%indiana.csnet@CSNET-RELAY.ARPA sentiments
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Date: Fri, 30 May 86 15:34:53 est
From: Kent Dybvig <dyb%indiana.csnet@CSNET-RELAY.ARPA>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: sentiments
Cc: jar@MC.LCS.MIT.EDU
I believe I must explain to you why I am as upset about internal-define
as I am. This report has been a long time in coming and as it approaches
its final form, it begins to look quite splendid. So much so that I
believe that its potential for generating converts will be quite
substantial. That was, in fact, one of its goals. However, we Schemer's
have had the freedom for several years of writing code for papers and
books in just about any dialect we felt the audience could/would follow.
Scheme has been a fabulous tool for that purpose. The simplicity of the
language and the elegance of its definition attracted us and I am sure
many of you towards it. How simple was it? In the presence of macro
expansion, we needed the following 4 special forms: "quote", "lambda",
"if", and "set!". Many implementations began to exist on micros. One
of my students, Mark Meyer, implemented an entire Scheme system including
engines, macros, a compiler, the run time support in 5k bytes on a
IBM PC. He did this as an undergraduate in the 5 weeks following my
undergraduate programming languages course. Now it was the case that
"set!" assigned to the closest lexical "rib" and we assumed that the
bottom rib had all known identifers assigned to either "unbound" or,
in the case of +, to some value. This really was simple. With this view,
define was merely an alias for set!. However, define's value was its
first argument and set!'s value was its second argument.
This is how things were prior to the Brandeis meeting. As I recall the
feeling at the Brandeis meeting most of us were willing to go along with
the idea of limiting the use of "define" internally to the semantics of
SI&CP. This was in the interest of good feeling about not undermining
their book. I hope everyone understands that I do not want to undermine
their book, although I would like to see them rewrite it without internal
defines. However, when I went along with this view I had underestimated
how damaging this decision would be to the characterization of Scheme being
a simple language. I was expecting a "comment" in the report that stated
that "use of define within the text of a program would be restricted to
the use as given in SI&CP." Instead, the definition of "lambda" got changed.
Instead, begin must be added to the list of special forms. Instead the
macro for "letrec" must be conscious of it by having the body be
"(let () <body>)" where it should be <body>. Instead define must be added to
the list of special forms. Instead the semantics of "set!" are weakened
so that it is not possible to just get by with "set!" and ignore "define".
Instead we must do something "special" with "lambda", "named-lambda",
"let", "let*", and "letrec".
We have taken a rather elegant language and made it elitest. I wanted
all of my students to be able to implement "Scheme" when they walked out
of my course, now that is no longer possible. It was a great beauty of
Scheme that the four mentioned special forms along with identifiers and
application were the only syntax. It was wonderful that a CPS interpreter
for Scheme was all that was necessary to come to grips with in order to
understand the run-time architecture of Scheme.
My argument with internal-define is not that it is good or bad, but
that the subtlety of its definition is unnecessary with judicious use
of letrec and letrec should be a trivial macro. What happened?
I have never liked internal defines. I thought they were harmless
until I saw what havoc they introduced to the Report. I am trying
desperately to convince everyone that we made a mistake and we should
do everything in our power before we go public on this Report to
wait until we impose internal defines on everyone.
Dan
∂31-May-86 1608 @MC.LCS.MIT.EDU:JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU sentiments
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Date: Sat, 31 May 86 18:53:02 EDT
From: Jonathan A Rees <JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU>
Subject: sentiments
To: dfried%indiana.csnet@CSNET-RELAY.ARPA
cc: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <[MX.LCS.MIT.EDU].923375.860531.JAR>
Date: Fri, 30 May 86 15:34:53 est
From: Dan Friedman
Sent-by: Kent Dybvig
... define was merely an alias for set! ...
This is how things were prior to the Brandeis meeting.
This is how things were AT INDIANA prior to the Brandeis meeting. At
Yale and MIT they somewhat different (although not as different as you
suppose) and had been since at least 1981. Your quest for elegance is
noble but please try not to equate your own version of Scheme with
Scheme.
As I recall the feeling at the Brandeis meeting most of us were
willing to go along with the idea of limiting the use of "define"
internally to the semantics of SI&CP. This was in the interest of
good feeling about not undermining their book. I hope everyone
understands that I do not want to undermine their book, although I
would like to see them rewrite it without internal defines.
However, when I went along with this view I had underestimated how
damaging this decision would be to the characterization of Scheme
being a simple language. I was expecting a "comment" in the report
that stated that "use of define within the text of a program would
be restricted to the use as given in SI&CP." Instead, the
definition of "lambda" got changed.
I don't understand. Is it really the case that S&ICP never ever uses
internal defines in the body of a lambda? I'll check. In any case, if
internal definitions exist at all, LAMBDA is the ONLY form that's
affected, after macro expansion.
Instead, begin must be added to the list of special forms.
Not true, and I'm don't understand why you think so. Note that I
clearly put BEGIN in the "derived expression types" section. I will
include the usual expansion of it in a future draft; I forgot to note
that this was on my list of things to do.
Instead the macro for "letrec" must be conscious of it by having the
body be "(let () <body>)" where it should be <body>.
I proposed flushing internal definitions in the body of a letrec for
exactly this reason. But I don't see this as increasing the complexity
of LETREC significantly, and I was wrong to draw attention to it. I'll
try to figure out how to make this smoother.
Instead define must be added to the list of special forms.
What do you mean? Definitions aren't even expressions!
Instead the semantics of "set!" are weakened so that
it is not possible to just get by with "set!" and ignore "define".
As has been explained innumerable times, there is no way to avoid this
and have a language which is at all coherent with T and MIT Scheme.
Note that in all programming languages of the Algol/Pascal/C variety it
is an error to assign to an undeclared variable. That MIT Scheme and T
(and thus RRRS Scheme) also have this property is not coincidence.
Instead we must do something "special" with "lambda",
"named-lambda", "let", "let*", and "letrec".
Certainly the report is muddled, and I must accept the blame for some of
this muddle. I introduced a lot of the nonsense you're complaining
about into this version of the report in a quest for accuracy. I agree
with your complaint that internal definitions are intrusive, and I'll do
what I can to remedy the situation.
We have taken a rather elegant language and made it elitest.
I don't understand this use of that term.
I wanted all of my students to be able to implement "Scheme" when
they walked out of my course, now that is no longer possible.
This is false. Internal defines are not essential. If by "Scheme" you
mean absolutely everything described in the report, I would expect that
internal definitions (which can be implemented with a very small amount
of code) would be the least of any implementor's worries. What about
number I/O?
It was a great beauty of
Scheme that the four mentioned special forms along with identifiers and
application were the only syntax. It was wonderful that a CPS interpreter
for Scheme was all that was necessary to come to grips with in order to
understand the run-time architecture of Scheme.
Why isn't this still true?
My argument with internal-define is not that it is good or bad, but
that the subtlety of its definition is unnecessary with judicious use
of letrec and letrec should be a trivial macro. What happened?
How do internal definitions make LETREC more complicated? The (LET ()
...) (which would otherwise be a (BEGIN ...)) is trivial compared to
the rest of what LETREC has to do, and doesn't even have to be there at
all if you're not implementing the full language.
I have never liked internal defines.
Thanks for telling me, I hadn't figured this out.
I thought they were harmless
until I saw what havoc they introduced to the Report. I am trying
desperately to convince everyone that we made a mistake and we should
do everything in our power before we go public on this Report to
wait until we impose internal defines on everyone.
I'll do what I can to fix the presentation; I can at least certainly
make internal definitions less intrusive than they were in the RRRS. I
hope that will be sufficient. Personally, I wouldn't mind removing
internal definitions from the language, although special treatment of
definitions at top level of a file (which is another story altogether)
must stay. If you can convince everyone, including Sussman and Abelson,
that internal definitions should be flushed, then I'll flush them. If
you must persue this, I suggest you talk to Sussman on the telephone
about this; he isn't reachable by electronic mail until June 20, I
think. I'll try to find his phone number at Princeton or HP or wherever
he is.
Why does this question arise at this moment? I am angered by the
untimeliness of this debate. Why didn't it come up when the idea of
printing the report in SIGPLAN was first mentioned? This part of the
language hasn't changed.
Jonathan
∂31-May-86 2319 @MC.LCS.MIT.EDU:JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU define -- a modest proposal
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From: Jonathan A Rees <JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU>
Subject: define -- a modest proposal
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Date: Fri, 30 May 86 10:40 EST
From: MITCHELL WAND <WAND%northeastern.edu at CSNET-RELAY.ARPA>
I think it is clear that we do not have a consensus on the semantics
of internal DEFINE.
This isn't clear to me. I thought we had always agreed that internal
definitions were just sugar for LETREC (see Will's message of 11 November
84, excerpted below).
My understanding of the compromise reached at
Brandeis was that lexically nested DEFINE would retain the MIT
semantics, whereas the IU semantics could be obtained by using
DEFINE! . The current report does not appear to be compatible with
that compromise, because it would appear necessary to do a
(define foo 'hunoz)
at top-level before one can legally do a set! on foo from an interior scope.
At first I thought that you had misremembered, but I just went back to
the archives, and you are right. However, DEFINE! was later flushed --
without any liberalization of SET! . The discussion was obviously
incomplete (as you can tell by reading it), and we're completing it now.
Will did the right thing since he flushed features that not everyone
wanted, namely (a) DEFINE! and (b) an environment in which SET! could
cause unbound variables to become bound. See the Appendix to this
message for the exchange.
I was moderately happy with how that turned out and implicitly assumed
that if people had serious troubles with the RRRS they would have spoken
up ages ago. My attempts to clarify things have apparently drawn
attention to issues which have been peacefully asleep for over a year.
Analyzing this situation, there are two operations involved in a define:
1. Binding the identifier to some location.
2. Storing a value in that location.
The latter operation is clearly doable by set!, so the only issue is #1.
The MIT semantics has DEFINE performing #1 on the current scope. The
advantage of this proposal is that it is uniform on both "top-level" and
interior scopes. The disadvantage is that it essentially creates a new scope
(region) in the program which is not delimited by parentheses.
This is true, the region is only the <body> of the LET or whatever
expression, not the entire expression, so the region isn't delimited by
left and right parentheses. The region of a definition at top level of
a file is similarly not delimited by parentheses, although for a
slightly different reason. I wouldn't say the definition creates the
scope, I'd say that the scope is created by the expression in whose body
the definition appears. But what is so unusual about this? The region
of a binding created by LET is also not delimited by parentheses; it's
not the entire LET expression.
[Perhaps the
grammar could be fixed to recognize this new, non-list-structure phrase?].
What change do you suggest? Why don't <body> and <program> foot the
bill? A <body> is exactly the region of the bindings specified by
internal definitions which begin it. A <program> (which, I suppose, is
the concatenation of all the files comprising a running Scheme program,
or something like that) is the region of bindings created by top level
definitions.
This is an unpleasantness at the top level which I do not think we
understand.
I guess I'm losing track of what you're saying. I agree that there is
much unpleasantness, but to which one are you referring?
In Algol 60 a <program> is a <block> or a <compound expression>, so
Algol 60 has the property you want, that regions are always fully
parenthesized (by BEGIN ... END). I always rationalized Scheme's lack
of "outermost parentheses" by the fact that there would be no point in
having them if you would always have to write them -- they would be
redundant. I imagine that those parentheses are there, just outside the
edge of my files, providing a region for my files' top level bindings to
live in. (The T compiler actually puts the parentheses there, treating
a file boundary as a sort of a macro.)
The main unpleasantness I see is the syntactic oddity that a <program>
is a sequence of intermixed <expression>s and <definition>s (it's very
important that <definition>s aren't <expression>s!), whereas a <body> is
a sequence of <definition>s followed by a sequence of <expression>s. I
think I suggested fixing this a while ago (whether to people at MIT or
to RRRS-Authors I don't remember), so that <program>s and <body>s could
have the same syntax and semantics (if internal definitions were
supported at all, that is), but this suggestion was not well received.
This change would make Scheme like Algol 68, which also allows one to
intersperse statements and declarations within a "series" (the region
("range") of a declaration includes previous statements and declarations
in its "series"). The other way to resolve the inconsistency is to be
like Algol 60 and require that all the definitions in a program go at
the top, before any statements (expressions), but somehow I don't think
people would buy that.
[Perhaps we should separate DEFINE into two procedures:
(make-local-variable 'foo)
(set! foo value)
A reasonable idea. In MIT Scheme, (make-local-variable 'foo) is written
(define foo). (Or do you really mean a procedure?) If people like this
feature (which causes the variable to become bound but unassigned, like
in LETREC) I'd be happy to see it go into the report. It is bothersome
that one has to specify an initial value, and this seems as good a way
as any to avoid having to do so.
[Another, separate, argument against including internal define as an
optional feature in the report is that, unlike the other optional
features in the report, it requires pervasive modifications in many
other sections of the report].
I agree that the presentation is bad. This is a real problem which, as
I said in my message to Dan, I think I can fix, by going back to
something closer to Will's approach, which was much less intrusive. I
take full responsibility for having screwed this up.
What I will argue for is the following:
An implementation may have a top level (initial, whatever) environment in
which every possible identifier is bound (though only some are initialized).
This would allow programs in that implementation to do a set! on a global
variable (excuse me, a variable in the current top-level environment)
[Can you define "current"?]
from an
internal scope without having to explicitly bind the variable in the initial
scope. It would also allow MIT-style define to proceed, as it does not
require the existence of a distinguished global environment.
I think this proposal retains the spirit of the Brandeis agreement on this
issue.
If people generally think it's OK if this is documented as an optional
language feature (as was DEFINE! previously), I don't have too much
problem with putting it in the report, if it's accompanied by some
mention of the fact that some implementations have principled reasons
for not having this feature. (Dan has complained to me, however, that
he doesn't want the report to contain advertisements for random features
of various dialects, so I wouldn't know quite how to do this.) My main
complaint is that it would be nice to be able to support as many as
possible of the report's non-essential features in T and MIT Scheme, and
it would be a substantial amount of work to implement this particular
feature in T and MIT Scheme; causing assigned variables to become bound
in an appropriate contour involves a bothersome non-local code
transformation.
The MIT Scheme and T designers have worked hard to implement truly
block-structured languages which, like Algol, have no distinguished
top-level environments. (Algol 68's "standard prelude" and its
mechanism of "particular-programs" is block structure to the max -- can
someone tell me what would correspond to the proposed SET! extension in
Algol 68?) Legitimizing binding-from-a-distance (or environments in
which all variables are bound, which amounts to the same thing) in the
Scheme report is a threat to the pedagogical and engineering effort
we've put in. Of course, de-legitimizing unprepared SET!'s is
apparently a threat to your investment. I thought the compromise in the
RRRS was a good one considering how different our world views were.
With apologies to you and Dan for the angry tone & the abundance of
parenthetical remarks. I'm tired.
Jonathan.
------
APPENDIX. Historical record of the DEFINE! and SET! debate.
Clinger, 11 Nov 84, preliminary report on the workshop:
(DEFINE id expr) allows top-level definitions of variables. Its
semantics at top level are similar to the semantics of
(SET! id expr). The difference is that if id is not already
bound to a location, then the DEFINE form binds id before
performing the assignment, whereas it would be a mistake to
perform a SET! on an unbound identifier.
Optionally, (DEFINE! id expr) is equivalent to (DEFINE id expr)
when typed at the top level. Within code, (DEFINE! id expr) is
equivalent to (SET! id expr) unless id is unbound, in which case
the DEFINE! form creates a new top level binding for id before
performing the assignment.
Optionally, DEFINE may be used for internal definitions as in MIT
Scheme and in the book by Abelson and Sussman. If allowed at
all, internal definitions are permitted only in the bodies of
LAMBDA, LET, LETREC, and similar binding constructs. Furthermore
they must precede the rest of the body. With these restrictions,
the semantics of internal definitions can be explained in terms
of LETREC. For example, ...
Pitman, 6 Dec 84:
The term "top-level binding" is ... completely vague in DEFINE!'s
definition.
Rees, 14 March 85:
... And incidentally, I don't remember the rationale for having both
DEFINE! and DEFINE. I understand why DEFINE shouldn't have hairy
syntax, but what does DEFINE! give you that the stripped-down DEFINE
doesn't?
Clinger, 18 March 85, "final" draft of report:
(define! var expr) special form
If var is bound, then the define! form is equivalent to the
corresponding set!. If var is unbound, however, define! binds
var in the global environment before performing the assignment.
Haynes and Friedman, 27 Mar 85:
DEFINE! and DEFREC! should go away. (Yes, We were among those who
wanted them originally, but they aren't worth it.) We're not fond of
DEFINE either and wish it could go the same way, or at least be
optional.
Bartley, 29 March 85:
I'm willing to lose DEFINE! and DEFREC!, as Chris and Dan suggest.
Rozas, 27 March 85:
How am I supposed to define things if both DEFINE! and DEFINE
go away?
Haynes, 29 March 85, answering Rozas:
With SET!, provided one assumes that all identifiers are initially bound in
the global environment, or that SET! can extend the global environment.
With the exception of MIT's Scheme, this is what existing systems do. If MIT
is unwilling to change this, then we are reluctantly stuck with DEFINE.
Hanson, 30 March 85, answering Haynes:
This is a terrible idea. It seems that the ability to have many
different environments in which to perform incremental definitions has
been consistently overlooked by almost everyone except MIT Scheme and
T. Anyone who has ever tried to program a BIG system, and by that I
mean something over 500-1000 pages of code, knows that this kind of
packaging is **ESSENTIAL**!! So please don't try to take this away.
Haynes, 31 March 85, answering Hanson:
We grant the importance of such a facility, and are not trying to take it
way; but there is no concensus on how to provide such a facility, so it
is too soon to standardize on one. (Similarly, syntactic extensions
are **ESSENTIAL** to the kind of thing we do here; but it is also too soon
to standardize on a syntactic extension mechanism.)
We were simply debating whether SET! should be required to extend the
global environment if its identifier is unbound (or equivalently, have
everything bound in the global environment to begin with). This would
make DEFINE unessential, though it might still be optional. It has
nothing to do with multiple environments for incremental definition,
except that MIT uses DEFINE for both purposes.
Hanson, 2 April 85, answering Haynes:
What I wanted to say was: if SET! extends the "global" environment,
then that environment has become special in that it is the ONLY
environment that can be extended by interactive definition. This
would seem to preclude the existence of many such environments.
DEFINE eliminates the problem, because it specifies, very precisely,
the environment in which the name is bound.
Clinger, 20 April 85:
define! and defrec! will be flushed altogether.
Note: no one at Indiana replied to Hanson's message, even though it
isn't conclusive. (I don't even think it's true; there could be
multiple "global" environments, and SET!'s could be associated with them
lexically.) Did they assume that SET! would be changed?
∂01-Jun-86 0815 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU define -- a modest proposal
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Date: 1 Jun 1986 11:10 EDT (Sun)
Message-ID: <JINX.12211357535.BABYL@MIT-OZ>
From: Bill Rozas <JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>
To: Jonathan A Rees <JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU>
Cc: rrrs-authors@MC.LCS.MIT.EDU, WAND%northeastern.edu@CSNET-RELAY.ARPA
Subject: define -- a modest proposal
In-reply-to: Msg of 1 Jun 1986 02:03-EDT from Jonathan A Rees <JAR%MX.LCS.MIT.EDU at MC.LCS.MIT.EDU>
In Algol 60 a <program> is a <block> or a <compound expression>, so
Algol 60 has the property you want, that regions are always fully
parenthesized (by BEGIN ... END). I always rationalized Scheme's lack
of "outermost parentheses" by the fact that there would be no point in
having them if you would always have to write them -- they would be
redundant. I imagine that those parentheses are there, just outside the
edge of my files, providing a region for my files' top level bindings to
live in. (The T compiler actually puts the parentheses there, treating
a file boundary as a sort of a macro.)
In MIT Scheme, the syntaxer (a program which translates s-expressions
into Scode, shared by the interpreter and the compiler) "puts" the
parantheses there by building an Scode object called an open-block
around the "top level".
The main unpleasantness I see is the syntactic oddity that a <program>
is a sequence of intermixed <expression>s and <definition>s (it's very
important that <definition>s aren't <expression>s!), whereas a <body> is
a sequence of <definition>s followed by a sequence of <expression>s. I
think I suggested fixing this a while ago (whether to people at MIT or
to RRRS-Authors I don't remember), so that <program>s and <body>s could
have the same syntax and semantics (if internal definitions were
supported at all, that is), but this suggestion was not well received.
This change would make Scheme like Algol 68, which also allows one to
intersperse statements and declarations within a "series" (the region
("range") of a declaration includes previous statements and declarations
in its "series"). The other way to resolve the inconsistency is to be
like Algol 60 and require that all the definitions in a program go at
the top, before any statements (expressions), but somehow I don't think
people would buy that.
I object to mixing internal definitions and expressions. I also
object to mixing top level definitions and expressions although I
admit to being guilty of laziness and occasionally doing the latter.
I never (as far as I can remember) mix them internally, and try to
avoid mixing top level ones also. I would not mind (and might even
applaud) a decision forcing top-level definitions to come first, which
would make the intenal and external cases more symmetric.
[Perhaps we should separate DEFINE into two procedures:
(make-local-variable 'foo)
(set! foo value)
A reasonable idea. In MIT Scheme, (make-local-variable 'foo) is written
(define foo). (Or do you really mean a procedure?) If people like this
feature (which causes the variable to become bound but unassigned, like
in LETREC) I'd be happy to see it go into the report. It is bothersome
that one has to specify an initial value, and this seems as good a way
as any to avoid having to do so.
It is completely unacceptable if it is a procedure (which was my
understanding given the wording and the QUOTE). This would imply
runtime definition (INCREMENTAL DEFINE), rather than static definition
(INTERNAL DEFINE). It also has the problem that if it is a procedure,
it needs the environment where the definition must occur as an
argument. Procedures cannot pick it up at run time.
If it is a special form, the QUOTE is not needed (nor the environment,
which is available at evaluation time), and it could be made static
(as I would expect everyone to want), but then it is exactly internal
DEFINE, so why change names?
I agree that (define foo) is reasonable, although only needed at top
level. I use it often in MIT-Scheme. In particular I use it as an
idiom indicating that the this variable is going to be assigned. I
specify an initial value only when it will not change. It is not
needed elsewhere (in MIT Scheme) because
(let ((foo))
...)
gives me a local binding for FOO which I can then assign.
Note: no one at Indiana replied to Hanson's message, even though it
isn't conclusive. (I don't even think it's true; there could be
multiple "global" environments, and SET!'s could be associated with them
lexically.) Did they assume that SET! would be changed?
JAR, I can't believe YOU have the bad taste to consider this (using
SET! to bind) seriously. One of the features that I dislike the most
from MacLisp and Franz (which is a poor clone of MacLisp), is that
SETQ is used to bind variables. I always use DEFCONST and DEFVAR
before assigning anything. Making this the standard (eliminating
DEFINE) would guarantee that I would never write in the standard
dialect. I'm sure that other people at MIT find this proposal as
distasteful as I do. I don't object to a system (like MacScheme, for
example) where SET! "works", but under no circumstances will I
accept a situation where it is the only way to do it. On such
systems, top-level DEFINE would be a NO-OP, which is fine with me, as
long as it is available.
∂01-Jun-86 2051 @MC.LCS.MIT.EDU:CPH@AI.AI.MIT.EDU schedule
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Date: Sun, 1 Jun 86 23:49:21 EDT
From: Chris Hanson <CPH@AI.AI.MIT.EDU>
Subject: schedule
To: JAR@AI.AI.MIT.EDU
cc: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Thu 29 May 86 14:36 EDT from Jonathan A Rees <JAR at MIT-AI.ARPA>
Message-ID: <[AI.AI.MIT.EDU].49879.860601.CPH>
I would vote for waiting a little longer before publishing, to get it
done right. It's not terribly important to me that it happen
immediately.
∂01-Jun-86 2343 @MC.LCS.MIT.EDU:dyb%indiana.csnet@CSNET-RELAY.ARPA Re: sentiments
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Date: Sun, 1 Jun 86 16:21:30 est
From: Kent Dybvig <dyb%indiana.csnet@CSNET-RELAY.ARPA>
To: jar@MC.LCS.MIT.EDU
Subject: Re: sentiments
Cc: dfried%indiana.csnet@CSNET-RELAY.ARPA, rrrs-authors@MC.LCS.MIT.EDU
Date: Fri, 30 May 86 15:34:53 est
From: Dan Friedman
Sent-by: Kent Dybvig
First, let me apologize that the note from Dan looked like it was
coming from me. I did "su dfried" and resent the note for him
after his first try failed. I thought that it would put his name
on the note. I also apologize for the length of this note, which
is due primarily to the fact that I have included the entirety of
Jonathan's response to Dan's note.
... define was merely an alias for set! ...
This is how things were prior to the Brandeis meeting.
This is how things were AT INDIANA prior to the Brandeis meeting. At
Yale and MIT they somewhat different (although not as different as you
suppose) and had been since at least 1981. Your quest for elegance is
noble but please try not to equate your own version of Scheme with
Scheme.
This is how things were in the first two Scheme reports, in several
Indiana Schemes, in one North Carolina Scheme, and probably in other
Schemes as well as of the Brandeis meeting.
As I recall the feeling at the Brandeis meeting most of us were
willing to go along with the idea of limiting the use of "define"
internally to the semantics of SI&CP. This was in the interest of
good feeling about not undermining their book. I hope everyone
understands that I do not want to undermine their book, although I
would like to see them rewrite it without internal defines.
However, when I went along with this view I had underestimated how
damaging this decision would be to the characterization of Scheme
being a simple language. I was expecting a "comment" in the report
that stated that "use of define within the text of a program would
be restricted to the use as given in SI&CP." Instead, the
definition of "lambda" got changed.
I don't understand. Is it really the case that S&ICP never ever uses
internal defines in the body of a lambda? I'll check. In any case, if
internal definitions exist at all, LAMBDA is the ONLY form that's
affected, after macro expansion.
I quickly scanned S&ICP and I found two uses of define within let
(pp. 234 and 238), and a mention of the use of a lambda-expression
translator to support internal definitions (p. 440). The obvious
implication to the thoughtful reader is that the authors intend to
allow definitions at the front of a lambda body; however, it might
also be reasonable to only effect "define" (and "let" if the few uses
are considered enough reason to complexify it).
Instead, begin must be added to the list of special forms.
Not true, and I'm don't understand why you think so. Note that I
clearly put BEGIN in the "derived expression types" section. I will
include the usual expansion of it in a future draft; I forgot to note
that this was on my list of things to do.
That begin must be a core special form results from the fact that in
the report, (begin (define ...) ...) must not open up a new scope;
i.e., (begin x y ...) must not be defined as ((lambda () x y ...)),
or the more traditional form ((lambda (t) (begin y ...)) x) where t
does not appear free in (begin y ...). I think of this as the "usual
expansion".
Instead the macro for "letrec" must be conscious of it by having the
body be "(let () <body>)" where it should be <body>.
I proposed flushing internal definitions in the body of a letrec for
exactly this reason. But I don't see this as increasing the complexity
of LETREC significantly, and I was wrong to draw attention to it. I'll
try to figure out how to make this smoother.
You are right, it is not much, but any added complexity is a shame,
especially when the added complexity is to support an innessential
feature (other than the one being described, of course).
Instead define must be added to the list of special forms.
What do you mean? Definitions aren't even expressions!
I wouldn't brag about this! Having already expanded Scheme from
expressions and functions to statements and procedures, we are now
adding declarations. What happened to simplicity?
Instead the semantics of "set!" are weakened so that
it is not possible to just get by with "set!" and ignore "define".
As has been explained innumerable times, there is no way to avoid this
and have a language which is at all coherent with T and MIT Scheme.
Note that in all programming languages of the Algol/Pascal/C variety it
is an error to assign to an undeclared variable. That MIT Scheme and T
(and thus RRRS Scheme) also have this property is not coincidence.
Algol, Pascal, and C are not (typically) interactive languages, nor
do they have such nice features as first-class functions that allow
one to form modules of functions sharing local state/help functions.
I think that it would be possible in any system to have a notion of
a "top-level" lexical environment which implicitly contains bindings
for all things not bound elsewhere. This could be a per-user or
per-module thing; it need not be the outermost lexical environment.
Instead we must do something "special" with "lambda",
"named-lambda", "let", "let*", and "letrec".
Certainly the report is muddled, and I must accept the blame for some of
this muddle. I introduced a lot of the nonsense you're complaining
about into this version of the report in a quest for accuracy. I agree
with your complaint that internal definitions are intrusive, and I'll do
what I can to remedy the situation.
We have taken a rather elegant language and made it elitest.
I don't understand this use of that term.
I don't either, but I think what he means is that only a handful of
experienced implementors will understand how a full Scheme system is
implemented.
I wanted all of my students to be able to implement "Scheme" when
they walked out of my course, now that is no longer possible.
This is false. Internal defines are not essential. If by "Scheme" you
mean absolutely everything described in the report, I would expect that
internal definitions (which can be implemented with a very small amount
of code) would be the least of any implementor's worries. What about
number I/O?
Dan was referring, I'm sure, to the core of the language, which he
feels must now not only include lambda, set!, quote, if, identifiers,
and applications but also begin and define, not to mention the added
complexity of lambda.
It was a great beauty of
Scheme that the four mentioned special forms along with identifiers and
application were the only syntax. It was wonderful that a CPS interpreter
for Scheme was all that was necessary to come to grips with in order to
understand the run-time architecture of Scheme.
Why isn't this still true?
My argument with internal-define is not that it is good or bad, but
that the subtlety of its definition is unnecessary with judicious use
of letrec and letrec should be a trivial macro. What happened?
How do internal definitions make LETREC more complicated? The (LET ()
...) (which would otherwise be a (BEGIN ...)) is trivial compared to
the rest of what LETREC has to do, and doesn't even have to be there at
all if you're not implementing the full language.
I think you misunderstood his point completely here. He was merely
wondering of what use internal define is if you have letrec, and noted
that you can get letrec trivially with lambda and set!, if you like.
I have never liked internal defines.
Thanks for telling me, I hadn't figured this out.
I thought they were harmless
until I saw what havoc they introduced to the Report. I am trying
desperately to convince everyone that we made a mistake and we should
do everything in our power before we go public on this Report to
wait until we impose internal defines on everyone.
I'll do what I can to fix the presentation; I can at least certainly
make internal definitions less intrusive than they were in the RRRS.
I hope that will be sufficient. Personally, I wouldn't mind removing
internal definitions from the language, although special treatment of
definitions at top level of a file (which is another story altogether)
must stay.
I agree in principle with this idea. It makes sense that define at
top level should be treated specially, and nested definitions such as
those given throughout S&ICP are quite handy and encourage modularity
in a nice way. Since this treatment would not affect lambda or let,
it would be easy to understand and easy to implement. I would agree
to using something totally different for definitions or perhaps use
the define/set! combinations for our interpretation of internal define
if we all agreed that define were only to be used at top level, with
the nested syntax. I would even agree to making top-level, nested
define a required feature, and to requiring that define not be used
anywhere else.
If you can convince everyone, including Sussman and Abelson,
that internal definitions should be flushed, then I'll flush them. If
you must persue this, I suggest you talk to Sussman on the telephone
about this; he isn't reachable by electronic mail until June 20, I
think. I'll try to find his phone number at Princeton or HP or wherever
he is.
Why does this question arise at this moment? I am angered by the
untimeliness of this debate. Why didn't it come up when the idea of
printing the report in SIGPLAN was first mentioned? This part of the
language hasn't changed.
We are all very sorry for the lateness of the debate, but it has
taken time to absorb everything (and we have brought it up before
publicly and privately, perhaps not as loudly). None of us had used
a system with the internal definitions until after the RRRS (not R3S)
came out, so we must plead a certain amount of ignorance in earlier
discussions. On the other hand, it is more important on the eve of
SIGPLAN publication than at any previous time, since that will be the
first wide distribution of a Scheme report, and we must come together
on this issue. We have an exceptionally tight community of people
working on/with Scheme and it is not good for us to put each other at
odds by publishing a feature that some of us strongly dislike in its
current form. We ask your forgiveness and patience; please realize
that we understand and very much appreciate all of your time and
effort that has gone gone into this report.
Jonathan
Kent
∂02-Jun-86 0730 @MC.LCS.MIT.EDU:JMILLER@OZ.AI.MIT.EDU Another Can of Worms?
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Date: 2 Jun 1986 10:28-EDT
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Subject: Another Can of Worms?
From: JMILLER@MIT-OZ
Reply-To: JMiller%OZ@MIT-MC
To: rrrs-authors@MC
Message-ID: <[MIT-OZ] 2-Jun-86 10:28:16.JMILLER>
I've withheld this one for a long time on the theory that new
problems with the language should be discussed AFTER the imminent
publication of the standard. Since we appear to have stalled
that yet again, I'd like to mention it.
I am very concerned about the fact that the document we are
promulgating as a language standard permits of no way to write
truly portable code. This arises from the lack of a convention
which would permit me to choose the names of variables which will
guarantee me that no implementation has used those names as
special forms. I know of two solutions: (a) a gentleman's
agreement to the effect that every implementation will support
some well-publicized mechanism for absorbing foreign portable
code (in MIT Scheme, for example, we could provide a portable
syntax table for this purpose); or (b) as in BCPL, make a formal
statement as part of the language design that certain names will
never be used as the names of built-in special forms.
I am in favor of option (b) since it prevents the current
implementors from becoming a select small clique which has more
knowledge than outsiders. One such proposal would be that we
insert a statement somewhere to the effect that "No
implementation shall supply by default a special form with ":" in
its name". Thus portable code uses variables with ":" in them
somewhere and all is well. [FYI, the BCPL statement was that
reserved words were all lower-case and more than one letter
long.]
-- Jim Miller
∂02-Jun-86 1558 @MC.LCS.MIT.EDU:JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU sentiments
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Date: Mon, 2 Jun 86 18:41:25 EDT
From: Jonathan A Rees <JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU>
Subject: sentiments
To: dyb%indiana.csnet@CSNET-RELAY.ARPA
cc: dfried%indiana.csnet@CSNET-RELAY.ARPA,
rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Sun 1 Jun 86 16:21:30 est from Kent Dybvig <dyb%indiana.csnet at CSNET-RELAY.ARPA>
Message-ID: <[MX.LCS.MIT.EDU].923886.860602.JAR>
Date: Sun, 1 Jun 86 16:21:30 est
From: Kent Dybvig <dyb%indiana.csnet at CSNET-RELAY.ARPA>
That begin must be a core special form results from the fact that in
the report, (begin (define ...) ...) must not open up a new scope;
i.e., (begin x y ...) must not be defined as ((lambda () x y ...)),
or the more traditional form ((lambda (t) (begin y ...)) x) where t
does not appear free in (begin y ...). I think of this as the "usual
expansion".
I get the feeling you haven't read the report. According to NEITHER
Will's RRRS, NOR the draft I sent out, is (begin (define ...) ...) a
syntactically valid expression! Look again at the BNF and at the text.
The usual expansion ((lambda (t) (begin y ...)) x) works perfectly well
since <expression> can't produce anything of the form (define ...),
<definition>s can only occur in <program>'s and <body>'s, and the syntax
of <sequence>s is (begin <expression>+), not (begin <body>). The RRRS
says that definitions are expressions, which isn't exactly wrong, but it
seemed a little misleading to me, since they aren't legitimate in all
places where expressions are supposed to be. (Again, only the details
of the description have changed, not the language described!)
Maybe you're misled by the statement in the RRRS that "(lambda (var1 ...)
expr1 expr2 ...) is equivalent to (lambda (var1 ...) (begin expr1 expr2
...))". This can be seen to be technically true if either (a) you take
this statement to be only about the essential subset or (b) definitions
aren't expressions (so that the statement wouldn't apply in the case of
(begin (define ...) ...)).
The BNF in the draft makes the error of classifying (begin ...) as
primitive instead of derived. This is an error. (At one point I too
was confused and thought that begin had to be primitive, but Sussman
straightened me out). Sorry if this bug confused you. I will fix it.
I wouldn't brag about this! Having already expanded Scheme from
expressions and functions to statements and procedures, we are now
adding declarations. What happened to simplicity?
"Now"? The fact that definitions weren't valid in copntexts other than
top level and the beginnings of "bodies" was agreed on Brandeis and
hasn't been challenged until now.
Introducing the term "statement" to mean an expression whose value is
thrown away seems harmless to me; I was inspired to do this by the
abstract syntax that Will sent me for the denotational semantics (which
sets Com = Exp). Using "<statement>* <expression>" instead of
"<expression>+" also gives a rationale for requiring at least one
expression in LAMBDA, BEGIN, etc. If there's general sentiment that
this is a bad idea, I'll flush it, but I thought it was reasonable.
We all know why we use "procedure" instead of "function". I don't
understand how this makes the language more complex.
Your question about simplicity is pure propaganda, so I won't answer it
beyond the above remarks.
As has been explained innumerable times, there is no way to avoid this
and have a language which is at all coherent with T and MIT Scheme.
Note that in all programming languages of the Algol/Pascal/C variety it
is an error to assign to an undeclared variable. That MIT Scheme and T
(and thus RRRS Scheme) also have this property is not coincidence.
Algol, Pascal, and C are not (typically) interactive languages, nor
do they have such nice features as first-class functions that allow
one to form modules of functions sharing local state/help functions.
I think that it would be possible in any system to have a notion of
a "top-level" lexical environment which implicitly contains bindings
for all things not bound elsewhere. This could be a per-user or
per-module thing; it need not be the outermost lexical environment.
I repeat: "there is no way to avoid [requiring that variables be bound
before they're assigned] and have a language which is at all coherent
with T and MIT Scheme." I never said it would be impossible to
implement. And interactiveness has nothing to do with it.
... I don't either, but I think what he means is that only a handful of
experienced implementors will understand how a full Scheme system is
implemented.
... Dan was referring, I'm sure, to the core of the language, which he
feels must now not only include lambda, set!, quote, if, identifiers,
and applications but also begin and define, not to mention the added
complexity of lambda.
Do I need to mail out a complete evaluator in order to drive the point
home?
I think you misunderstood his point completely here. He was merely
wondering of what use internal define is if you have letrec, and noted
that you can get letrec trivially with lambda and set!, if you like.
No one ever said internal defines were linguistically necessary. They
are obviously redundant. They are there because it's very important to
be compatible with something so central to S&ICP. Like I say, talk to
Sussman and Abelson if you dispute this.
I agree in principle with this idea. It makes sense that define at
top level should be treated specially, and nested definitions such as
those given throughout S&ICP are quite handy and encourage modularity
in a nice way. Since this treatment would not affect lambda or let,
it would be easy to understand and easy to implement.
How does its not affecting lambda or let have anything to do with how
easy it is to implement? Implementing internal defines involves one
trivial loop, and it doesn't matter whether you put this loop in the
code for lambda or define, although it DOES matter if you have to invoke
it two places.
I would agree
to using something totally different for definitions or perhaps use
the define/set! combinations for our interpretation of internal define
if we all agreed that define were only to be used at top level, with
the nested syntax. I would even agree to making top-level, nested
define a required feature, and to requiring that define not be used
anywhere else.
I don't understand this paragraph at all. Note that no one has ever
wanted internal defines to be essential in any context.
... We have an exceptionally tight community of people
working on/with Scheme and it is not good for us to put each other at
odds by publishing a feature that some of us strongly dislike in its
current form.
Like I say, talk to Abelson and Sussman. I think a lot has and can be
done to make internal definitions minimally ugly and intrusive. It is
not good to confuse many innocent bystanders and put your community at
odds with MIT's by permitting an incompatible meaning for DEFINE.
Jonathan.
∂02-Jun-86 1604 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA DEFINE -- a concrete proposal
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To: rrrs-authors@MC.LCS.MIT.EDU
Cc: jar%mx.lcs.mit.edu@MC.LCS.MIT.EDU, wand%northeastern.edu@CSNET-RELAY.ARPA,
dfried%indiana.csnet@CSNET-RELAY.ARPA
Subject: DEFINE -- a concrete proposal
Date: 02 Jun 86 13:23:55 PDT (Mon)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
I propose that section 4.1.0 of the 22 May 1986 draft be clarified to
read as follows:
At the top level of a program, a definition
(define <variable> <expression>)
has essentially the same effect as the assignment expression
(set! <variable> <expression>)
if <variable> is bound. If <variable> is not bound, however,
then the definition will bind <variable> before performing
the assignment, whereas it would be an error to perform a
set! on an unbound variable.
[examples go here]
Top level definitions are essential; all Scheme implementations
must support them.
Some implementations of Scheme use an initial environment in
which all possible variables are bound to locations, most of
which contain undefined values. Top level definitions in
such an implementation are truly equivalent to assignments.
In my opinion, this is merely a clarification because the draft
does not say that the initial environment must contain only the
variables mentioned in the report, and it is in fact the case
that most implementations supply variables that don't appear
in the report. Furthermore, even if unbound variables exist,
the phrase "it would be an error" indicates that implementations
are not required to complain when one is assigned, so an
implementation is free to do something random (like bind the
variable and do an assignment) instead of signalling the error.
The phrase "Some implementations of Scheme" is the very same
neutral phrase used at the beginning of Section 4.2 on internal
definitions. Thus the report would be neutral between those
who for whatever reason want to assign variables before they
declare them and those who for whatever reason prefer the
internal definition syntax to LETREC.
Since this is only a clarification of what is already implicit
in the report, I believe this proposal should satisfy those who
prefer the status quo. I believe it should also satisfy those
who with Mitch are arguing for the following:
An implementation may have a top level (initial, whatever)
environment in which every possible identifier is bound
(though only some are initialized).
This would allow programs in that implementation to do a set!
on a global variable (excuse me, a variable in the current
top-level environment) from an internal scope without having
to explicitly bind the variable in the initial scope. It would
also allow MIT-style define to proceed, as it does not require
the existence of a distinguished global environment.
Mitch is entirely right that his proposal retains the spirit of
the Brandeis agreement on this issue. Though Jonathan said in
his reply to Mitch that he wouldn't have too much problem with
adding this clarification to the report, he insisted that it should
be "accompanied by some mention of the fact that some implementations
have principled reasons for not having this feature". I say that
stipulation is unfair -- the report doesn't contain any of the
principled arguments against internal definitions or against the
fancy DEFINE syntax or against REC or against NAMED-LAMBDA or
against NIL or against the behavior of EQ? on procedures or
against hexadecimal notation...
Dan Friedman had some very reasonable things to say about the
importance of simplicity and elegance, particularly with regard
to ease of implementation by students. My answer is that
students should implement "Essential Scheme" instead of worrying
about how to get ASIN to work with complex numbers. Essential
Scheme does not have internal definitions, and it is perfectly
all right to use an initial environment in which all variables
are bound and to implement DEFINE as assignment.
I must admit that Essential Scheme is a more elegant language than
full Scheme.
I second Bill Rozas's objections to MAKE-LOCAL-VARIABLE as a procedure
for performing incremental definitions.
Let us seek peace,
William Clinger
----------------------------------------------------------------
[Because of one mailer error, the local postmaster has suggested
that people send me mail at willc@tekchips.tek.csnet instead of
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∂02-Jun-86 1803 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: definitions; APPEND!; etc
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Date: Mon 2 Jun 86 18:46:15-CDT
From: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: Re: definitions; APPEND!; etc
To: willc%tekchips.tek@CSNET-RELAY.ARPA,
rrrs-authors%mc.lcs.mit.edu@CSNET-RELAY.ARPA
Cc: jar%mc.lcs.mit.edu@CSNET-RELAY.ARPA, Bartley%TI-CSL@CSNET-RELAY.ARPA,
605301901283@tekchips
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[Bartley:]
>>APPEND! always side-effects all but its last argument.
[Clinger:]
>No, APPEND! should not be required to perform side effects. This is not
>as silly as it may sound. In an implementation using the Hewitt-Lieberman
>gc algorithm, for example, side effects to sufficiently old structures are
>likely to be more expensive than consing. APPEND! should be free to decide
>for itself which technique is fastest.
My point of view is that APPEND! is used to ensure sharing of
structure and APPEND is used to ensure that structure is NOT shared
(except in the clearly specified case of the last argument).
>I would feel differently if APPEND! returned an unspecified value, as
>does VECTOR-SET!.
Perhaps that would be more consistent. Perhaps we should call it
SET-LAST-CDR! instead!
Seriously, I could go either way, but I'm sure some of my code would
fail to work on a system in which APPEND! did not share structure.
Are there any others we should be discusssing?
--db--
-------
∂03-Jun-86 0853 @MC.LCS.MIT.EDU:Asrivastava%ti-csl.csnet@CSNET-RELAY.ARPA
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Date: Tue, 3 Jun 86 11:06:15 cdt
From: John Maeda <maeda%tilde%ti-csl.csnet@CSNET-RELAY.ARPA>
To: jkr%mit-oz@MC.LCS.MIT.EDU
okay glen I hope this gets to you; I had written you a real l ong letter but
I have no idea how to save it from this version of EMACS running on this uLTRIX
machine ... (must be a ti-professional playing "multi-user") ... so I'm really
ticked, I just hope this gets to you.
jtm
∂03-Jun-86 0953 @MC.LCS.MIT.EDU:JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU APPEND!
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Date: Tue, 3 Jun 86 12:37:27 EDT
From: Jonathan A Rees <JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU>
Subject: APPEND!
To: Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
cc: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Mon 2 Jun 86 18:46:15-CDT from David Bartley <Bartley%ti-csl.csnet at CSNET-RELAY.ARPA>
Message-ID: <[MX.LCS.MIT.EDU].924078.860603.JAR>
Maybe we should just flush APPEND! altogether? It's easy enough to do
(SET-CDR! (LAST-PAIR list1) list2). I think Sussman was the one who
really wanted APPEND! in the language, but I forget why.
Jonathan
∂03-Jun-86 1010 @MC.LCS.MIT.EDU:JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU portability
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Date: Tue, 3 Jun 86 13:08:20 EDT
From: Jonathan A Rees <JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU>
Subject: portability
To: RRRS-AUTHORS@MX.LCS.MIT.EDU
Message-ID: <[MX.LCS.MIT.EDU].924086.860603.JAR>
The following is in response to Jim Miller's message about portability,
which raises an important question I've been hoping to repress. But Freud
tells us that the repressed always returns.
- Jonathan
Date: Sat, 31 May 86 21:32:00 EDT
From: Jonathan A Rees <JAR%MX.LCS.MIT.EDU at MC.LCS.MIT.EDU>
To: GJC%MX.LCS.MIT.EDU at MC.LCS.MIT.EDU
cc: JAR at MX.LCS.MIT.EDU
Re: revised↑n report
In-reply-to: Msg of Sat 31 May 86 13:16:32 EDT from George J. Carrette <GJC%MX.LCS.MIT.EDU at MC.LCS.MIT.EDU>
Message-ID: <[MX.LCS.MIT.EDU].923398.860531.JAR>
Date: Sat, 31 May 86 13:16:32 EDT
From: George J. Carrette <GJC%MX.LCS.MIT.EDU at MC.LCS.MIT.EDU>
To: JAR%MX.LCS.MIT.EDU at MC.LCS.MIT.EDU
One should be able to show that clever underspecification in
a language spec is eventually a losing proposition. Example:
in CL (make-array 3) => #(0 0 0) (e.g. in VAX-NIL) or #(NIL NIL NIL)
in at least the LISPM environments I'm aware of. The idea
is to make the guy say (make-array <x> :initial-element <value>) if
he is depending on the initial value. Supposed to be a big efficiency
win. (now, I've just spent a few hours tracking down a bug in the
DOE-MACSYMA plot package that had to do with the initial element of
an array screw). A few days ago you had a note to the CL list about
a similar underspecification screw in defstruct.
Well, revised↑n has its share of clever underspecification too.
But, is this really a win in a language spec? Or is it just a way
of showing (forcing down everybodies neck...) how much the
language designers know about different implementation tricks?
You dont see this kind of stuff in other language specs.
Back to the array example. Is it reasonable to argue that in lisp
there are good natural default values? The empty list as default
for an array? I think it is. On the other hand, if you know that
there might be machine dependancies in these defaults, (in fact it
is usually operating system dependancies. VMS goes to some trouble to
make sure pages allocated to users are filled with zero's)
then why not have:
(make-array 10 :initial-element *:system-prefered-initial-array-element).
I argue that clever underspecifications for the purpose of elicidating
implementation tricks know by the language designers causes:
* "dating" of the language.
* frustration for users of the language
* eventual lack of portability.
This is all too true. I think that if I were designing another language
now I would try to get rid of all underspecifications, since they lead
to so much confusion. I hope that as many underspecifications as
possible will disappear from Common Lisp.
Let me try to figure out why I think it's OK for Scheme to be
underspecified and not for Common Lisp to be underspecified. Scheme's
underspecifications don't generally have anything to do with
"implemetation tricks." Political expediency demands that the report
leave a lot of room for local variation. We wouldn't be able to get
agreement on all these little things. Some differences between versions
result from differing implementation demands, but mostly it's that the
different groups have incompatible ideologies, so each group would have
its own idea of what the "right" thing is for each situation.
The goals of Revised↑n Scheme differ from those of Common Lisp, I think.
Mostly we want to be able to read each others' code when it appears in
the literature, and relieve people from the pain of there being
incompatible languages all calling themselves "scheme". Portability is
only a secondary consideration, and we're not so concerned that all
non-erroneous programs should port, only that "well-written" programs
should port. I think there's the feeling that people who write in
Scheme don't just play around until their code just happens to work
(often the only programming technique available in some systems which
will remain nameless) -- they actually write "clean" code which observes
data abstractions and doesn't depend on things it shouldn't depend on
(like the initial value of vector components). So while it's very easy
to write unportable code, people who do so have somehow missed the
point, and probably ought to be programming in CLU or Ada (or the
language I have yet to design?) instead.
If we really want to aim for airtight portability then we've got to start
making a lot of changes.
Jonathan.
∂03-Jun-86 1124 @MC.LCS.MIT.EDU:WAND%northeastern.edu@CSNET-RELAY.ARPA define
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Date: Tue, 3 Jun 86 11:29 EST
From: MITCHELL WAND <WAND%northeastern.edu@CSNET-RELAY.ARPA>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: define
1. I think the discussion has clarified, at least for me, the difference
between "internal" and "incremental" define. I was certainly thinking about
"incremental" define, which happens conceptually at run-time. As I gather it,
the idea is that internal define is JUST SYNTAX, which might be formalized as
something like
(define-equivalent-syntax ;; hypothetical pseudocode!
(<context-for-internal-define>
(define name1 body1) ...
<body>)
(letrec
((name1 body1) ...)
<body>))
The only place where "internal" define acts truly incrementally is at the top
level.
If this is correct, then my objections are considerably lessened. The major
complication of internal define, then, is sorting out in exactly which
contexts this syntax is permissable. This is a matter on which I think there
can be reasoned debate.
2. Will's proposal looks OK to me.
3. (make-local-variable 'foo) was a joke. No one seemed to get it. Sorry
'bout that.
4. Thanks to jinx and to jar for their thoughtful replies. In particular
thanks to jar (I think) for extracting the historical record. I say "jar (I
think)" because I've managed to lose my copy ($%↑&! VMS mailer); could someone
retransmit it? Tnx.
Mitch
∂03-Jun-86 1441 @MC.LCS.MIT.EDU:Asrivastava%ti-csl.csnet@CSNET-RELAY.ARPA SCOOPS source
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Date: Tue 3 Jun 86 15:32:49-CDT
From: Amitabh Srivastava <Asrivastava%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: SCOOPS source
To: scheme%mc.lcs.mit.edu@CSNET-RELAY.ARPA
Cc: Asrivastava%ti-csl.csnet@CSNET-RELAY.ARPA
Message-Id: <12211940524.20.ASRIVASTAVA@CSC60>
SCOOPS source is available now. It can be obtained by doing anonymous
ftp at host BBNA to the directory PS:<TICSL.RELSCOOPS> .
Initially, ftp the file README.SCM . It contains list of the
files needed and other information. The sources have been modified
and are totally in TI Scheme.
- amitabh
-------
∂03-Jun-86 1554 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Is BEGIN primitive?
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To: jar%mx.lcs.mit.edu@MC.LCS.MIT.EDU, dyb%indiana.csnet@CSNET-RELAY.ARPA
Cc: rrrs-authors@MC.LCS.MIT.EDU
Subject: Is BEGIN primitive?
Date: 03 Jun 86 10:04:25 PDT (Tue)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
Whether you think BEGIN must be a primitive expression depends on your
cultural heritage. If you have grown up believing that syntax is fully
checked before macro expansion, then (BEGIN X Y ...) ==>
((LAMBDA () X Y ...)) works fine. If you have grown up believing that
macros do the least amount of syntax checking they can get away with
(or less), then (BEGIN (DEFINE ...) ...) ==> ((LAMBDA () (DEFINE ...) ...))
does not detect the syntax error.
I like the term "derived expression" because it expresses the fact that
the semantics of BEGIN can be expressed in terms of primitive expressions
without implying that a macro mechanism is used.
Though the word "statement" ought to signify a declarative assertion,
the American programming language community long ago corrupted it to
signify a command. I prefer the English "command", but I prefer even
"statement" to the phrase "expression evaluated solely for effect".
Peace, Will
∂03-Jun-86 2023 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU ftp-able r3rs.dvi
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Date: Tue, 3 Jun 86 23:21 EDT
From: Jonathan A Rees <JAR@MIT-AI.ARPA>
Subject: ftp-able r3rs.dvi
To: rrrs-authors@MIT-MC.ARPA
Message-ID: <860603232145.2.JAR@ROCKY-GRAZIANO.LCS.MIT.EDU>
I put the DVI file for the report on host MIT-PREP. The filename
is
/u/jar/r3rs.dvi
- Jonathan
∂04-Jun-86 0554 @MC.LCS.MIT.EDU:JMILLER@OZ.AI.MIT.EDU Re: portability
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Date: 4 Jun 1986 08:51-EDT
Sender: JMILLER@MIT-OZ
Subject: Re: portability
From: JMILLER@MIT-OZ
Reply-To: JMiller%OZ@MC
To: RRRS-Authors@MC
Message-ID: <[MIT-OZ] 4-Jun-86 08:51:16.JMILLER>
In-Reply-To: <[MX.LCS.MIT.EDU].924086.860603.JAR>
Well, I agree in principle with all that was said. But I think
you have missed one important point: it is not possible, even
with all the care in the world, to write portable code in the
current design. I don't want to contort the language design in
any way (and neither of my suggestions do that) but I DO want
some statement which makes the possibility of portable code
feasible.
I urge you to think, again, about including some formal and
mutually agreeable statement which limits the implementors choice
of names for special forms. I believe that this is the sole
requirement necessary to permit a person intent on writing a
totally portable program to succeed.
--Jim
∂04-Jun-86 1049 @MC.LCS.MIT.EDU:Asrivastava%ti-csl.csnet@CSNET-RELAY.ARPA Re: SCOOPS source
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Date: Wed 4 Jun 86 11:47:42-CDT
From: Amitabh Srivastava <Asrivastava%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: Re: SCOOPS source
To: scheme%mc.lcs.mit.edu@CSNET-RELAY.ARPA
Cc: Asrivastava%ti-csl.csnet@CSNET-RELAY.ARPA
In-Reply-To: <12211940524.20.ASRIVASTAVA@CSC60>
Message-Id: <12212161685.28.ASRIVASTAVA@CSC60>
I am sorry - our systems people blew it. BBNA does not allow
user anonymous. The sources are available on host UTEXAS-20
in the directory ps:<g.ti.scoops> . Use anonymous ftp to get the
sources.
Initially, ftp the file README.SCM . It contains list of the
files needed and other information. The sources have been modified
and are totally in TI Scheme.
Again, my apologies for this confusion.
- amitabh
-------
∂04-Jun-86 1623 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: portability
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To: JMiller%OZ@MC.LCS.MIT.EDU
Cc: RRRS-Authors@MC.LCS.MIT.EDU
Subject: Re: portability
In-Reply-To: Your message of 4 Jun 1986 08:51-EDT.
<[MIT-OZ] 4-Jun-86 08:51:16.JMILLER>
Date: 04 Jun 86 09:51:03 PDT (Wed)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
Jim Miller writes:
>I urge you to think, again, about including some formal and
>mutually agreeable statement which limits the implementors choice
>of names for special forms. I believe that this is the sole
>requirement necessary to permit a person intent on writing a
>totally portable program to succeed.
Suppose every implementation of Scheme were required to supply a
"vanilla" mode in which all reserved words are among those that
appear in the report?
Peace, Will
∂05-Jun-86 0546 @MC.LCS.MIT.EDU:JMILLER@OZ.AI.MIT.EDU Re: portability
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Date: 5 Jun 1986 08:42-EDT
Sender: JMILLER@MIT-OZ
Subject: Re: portability
From: JMILLER@MIT-OZ
Reply-To: JMiller%OZ@MC
To: RRRS-Authors@MC
Message-ID: <[MIT-OZ] 5-Jun-86 08:42:33.JMILLER>
In-Reply-To: <8606041651.AA28499@tekchips>
I'd be happy with Will's suggestion, and it does make the writing
of portable code considerably easier than my suggestion. I'm
only concerned that this may require unanimous consent. I
believe that the MIT system already includes the necessary hooks
(we would supply an RRRS-Essential syntax table).
--Jim
∂05-Jun-86 0935 @MC.LCS.MIT.EDU:dfried%indiana.csnet@CSNET-RELAY.ARPA Will's proposal
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Date: Wed, 4 Jun 86 23:44:17 est
From: Dan Friedman <dfried%indiana.csnet@CSNET-RELAY.ARPA>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: Will's proposal
We are satisfied with Will's proposal re "set!".
Dan
∂05-Jun-86 0939 @MC.LCS.MIT.EDU:dfried%indiana.csnet@CSNET-RELAY.ARPA named-lambda and rec
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Date: Wed, 4 Jun 86 23:47:27 est
From: Dan Friedman <dfried%indiana.csnet@CSNET-RELAY.ARPA>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: named-lambda and rec
Jinx recently suggested that he could live without either.
I second jinx's suggestion.
Dan
∂05-Jun-86 1055 @MC.LCS.MIT.EDU:CPH@AI.AI.MIT.EDU named-lambda and rec
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Date: Thu, 5 Jun 86 13:54:25 EDT
From: Chris Hanson <CPH@AI.AI.MIT.EDU>
Subject: named-lambda and rec
To: dfried%indiana.csnet@CSNET-RELAY.ARPA
cc: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Wed 4 Jun 86 23:47:27 est from Dan Friedman <dfried%indiana.csnet at CSNET-RELAY.ARPA>
Message-ID: <[AI.AI.MIT.EDU].52205.860605.CPH>
Date: Wed, 4 Jun 86 23:47:27 est
From: Dan Friedman <dfried%indiana.csnet at CSNET-RELAY.ARPA>
Jinx recently suggested that he could live without either.
I second jinx's suggestion.
I `third' it.
∂06-Jun-86 0800 @MC.LCS.MIT.EDU:JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU portability
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Date: Fri, 6 Jun 86 10:59:26 EDT
From: Jonathan A Rees <JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU>
Subject: portability
To: JMiller@OZ.AI.MIT.EDU
cc: RRRS-Authors@MC.LCS.MIT.EDU
In-reply-to: Msg of 5 Jun 1986 08:42-EDT from JMILLER at MIT-OZ
Message-ID: <[MX.LCS.MIT.EDU].924918.860606.JAR>
I would say that a strict reading of the new draft, and perhaps even of
the RRRS, would say that ANY identifier other than those explicitly
listed as syntactic keywords (reserved words) may be used as a variable.
In other words, a correct implementation of the report would already
have the property that there are no other special forms other than the
ones explicitly listed in the report (the complete list is somewhere
inside the BNF). So that a program which does (define trace ...) or
(let ((loop ...)) ... (loop ...) ...) would already be portable. The
addition of ANY special form is an incompatible change to Scheme.
[Actually, if in a particular implementation special-form-ness is
cancelled out by DEFINE and lambda-binding, then it would probably be OK
in that implementation to have extra special forms/macros lying around,
since a program which used those identifiers for variables would still
be correct. But let's not think about this possibility.]
I wouldn't say that all implementations would have to start up with the
stripped-down syntax, omitting all their favorite features, but I think
that supplying a mode in which this was the case, rather than saying
only a certain class of identifiers can be used as variables, is the
right thing.
Would any implementors have any problem providing a report-syntax-only
mode? I know this is trivial in MIT Scheme and T, but we haven't heard
from other implementors.
If there are problems, then one way to cope would be to add to the
report's list of syntactic keywords some or all of the things which such
implementations would like to have be special forms, e.g. define-macro,
trace, make-environment, etc., simply saying that these are reserved for
use by particular implementations as syntactic keywords, but have no
meaning according to the report. This is sort of the dual of Jim's
original suggestion. It's pretty gross, but I thought I'd mention it.
How should this situation be explained in the report, if at all?
Jonathan
∂06-Jun-86 0806 @MC.LCS.MIT.EDU:dfried%indiana.csnet@CSNET-RELAY.ARPA add1 and sub1
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Date: Fri, 6 Jun 86 09:57:13 est
From: Dan Friedman <dfried%indiana.csnet@CSNET-RELAY.ARPA>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: add1 and sub1
When describing arithmetic I find the symbols "1+" and
"-1+" very harmful. The function + is denoted by the
symbol "+" and this confuses people who are trying to
understand the primitive recursive definition of +.
Purely for pedagogical reasons I would like to see "add1"
and "sub1" be optional. I know that macscheme & PC-Scheme
have included them. I don't like multiple names for the
same construct, but we have a few instances already in the
report.
Dan
∂06-Jun-86 1039 @MC.LCS.MIT.EDU:CPH@AI.AI.MIT.EDU add1 and sub1
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Date: Fri, 6 Jun 86 13:38:45 EDT
From: Chris Hanson <CPH@AI.AI.MIT.EDU>
Subject: add1 and sub1
To: dfried%indiana.csnet@CSNET-RELAY.ARPA
cc: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Fri 6 Jun 86 09:57:13 est from Dan Friedman <dfried%indiana.csnet at CSNET-RELAY.ARPA>
Message-ID: <[AI.AI.MIT.EDU].52665.860606.CPH>
Date: Fri, 6 Jun 86 09:57:13 est
From: Dan Friedman <dfried%indiana.csnet at CSNET-RELAY.ARPA>
When describing arithmetic I find the symbols "1+" and
"-1+" very harmful.
Purely for pedagogical reasons I would like to see "add1"
and "sub1" be optional.
Another alternative might be to make `1+' and `-1+' optional, since
they aren't necessary in any sense. Then there would be no need to
describe them to students at all.
In fact, there's no need to teach them even if they are essential.
∂06-Jun-86 2038 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: portability
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Date: Fri 6 Jun 86 13:55:31-CDT
From: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: Re: portability
To: JAR%MX.LCS.MIT.EDU%mc.lcs.mit.edu@CSNET-RELAY.ARPA,
JMiller%oz.ai.mit.edu@CSNET-RELAY.ARPA
Cc: RRRS-Authors%mc.lcs.mit.edu@CSNET-RELAY.ARPA, Bartley%TI-CSL@a
In-Repl <[MX.LCS.MIT.EDU].924918.860606.JAR>
Message-ID: <12212709243.41.BARTLEY@CSC60>
From JAR:
>I would say that a strict reading of the new draft, and perhaps even of
>the RRRS, would say that ANY identifier other than those explicitly
>listed as syntactic keywords (reserved words) may be used as a variable.
>In other words, a correct implementation of the report would already
>have the property that there are no other special forms other than the
>ones explicitly listed in the report (the complete list is somewhere
>inside the BNF). So that a program which does (define trace ...) or
>(let ((loop ...)) ... (loop ...) ...) would already be portable. The
>addition of ANY special form is an incompatible change to Scheme.
Several implementations, including Chez Scheme, PC Scheme, and
Scheme-84, allow user-specified syntactic extensions. I doubt if we
could get a consensus that this is to be disallowed. When you (JAR)
speak of special forms, are you including macros and the like?
>[Actually, if in a particular implementation special-form-ness is
>cancelled out by DEFINE and lambda-binding, then it would probably be OK
>in that implementation to have extra special forms/macros lying around,
>since a program which used those identifiers for variables would still
>be correct. But let's not think about this possibility.]
Is there an alternative possibility?
(This paragraph seems to say that you are speaking of macros as well
as special forms.)
Regards,
David Bartley
-------
∂07-Jun-86 1658 @MC.LCS.MIT.EDU:dfried%indiana.csnet@CSNET-RELAY.ARPA macros.
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Date: Sat, 7 Jun 86 15:25:24 est
From: Dan Friedman <dfried%indiana.csnet@CSNET-RELAY.ARPA>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: macros.
Our programming relies heavily on the safe use of macros.
No one here would be willing to remove the option of having
them in the language.
Dan
∂07-Jun-86 1820 @MC.LCS.MIT.EDU:adams%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: named-lambda and rec
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Date: Fri, 6 Jun 86 09:11:02 PDT
From: Norman Adams <adams%tekchips.tek.csnet@CSNET-RELAY.ARPA>
Message-Id: <8606061611.AA26553@tekchips>
Subject: Re: named-lambda and rec
To: rrrs-authors@MC.LCS.MIT.EDU
In-Reply-To: Dan Friedman <dfried%indiana.csnet@csnet-relay.arpa>, Wed, 4 Jun 86 23:47:27 est
I too would prefer to see both NAMED-LAMBDA and REC removed.
-Norman
-------
∂07-Jun-86 1829 @MC.LCS.MIT.EDU:dyb%indiana.csnet@CSNET-RELAY.ARPA Re: add1 and sub1
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Date: Fri, 6 Jun 86 15:43:12 est
From: Kent Dybvig <dyb%indiana.csnet@CSNET-RELAY.ARPA>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: Re: add1 and sub1
Another alternative might be to make `1+' and `-1+' optional, since
they aren't necessary in any sense. Then there would be no need to
describe them to students at all.
These are already innessential, in both RRRS and the draft RRRRS.
Chez Scheme will support add1 and sub1 for Dan (and the Little LISPer),
but I don't care if they appear in the report or not. I will also support
1- as an alternative for -1+; if ever there was a gratuitous difference
from Common Lisp, -1+ is it. Actually, I'd prefer flushing 1+ and -1+
from the report, but it doesn't seem worth worrying about.
∂08-Jun-86 1652 @MC.LCS.MIT.EDU:Swenson.Multics@MIT-MULTICS.ARPA Re: SCOOPS source
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Acknowledge-To: "Eric J. Swenson" <Swenson@MIT-MULTICS.ARPA>
Date: Sun, 8 Jun 86 19:35 EDT
From: "Eric J. Swenson" <Swenson@MIT-MULTICS.ARPA>
Subject: Re: SCOOPS source
To: Amitabh Srivastava <Asrivastava%ti-csl.csnet@CSNET-RELAY.ARPA>
cc: scheme%mc.lcs.mit.edu@CSNET-RELAY.ARPA
In-Reply-To: Message of 3 Jun 86 16:32 EDT from "Amitabh Srivastava"
Message-ID: <860608233557.811290@MIT-MULTICS.ARPA>
Are you certain BBNA supports anonymous FTP? I repeatedly get rejected
when attempting to "login anonymous" with an error indicating that there
is no such user as "anonymous."
∂09-Jun-86 1643 @MC.LCS.MIT.EDU:JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU portability
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Date: Mon, 9 Jun 86 19:27:34 EDT
From: Jonathan A Rees <JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU>
Subject: portability
To: Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
cc: RRRS-AUTHORS@MX.LCS.MIT.EDU
Message-ID: <[MX.LCS.MIT.EDU].925333.860609.JAR>
OK, my message seems to have confused a lot of people. I'll try to be
clearer. For the purposes of this message I'll only consider
system-supplied special form types, not user-supplied ones, although the
problems are I think the same.
Jim Miller said originally that he didn't see any way to write portable
programs which used variables, because implementations were free to
preempt arbitrary variable names for use as syntactic keywords. I just
wanted to reply that on the contrary, the report is clear on what the
set of allowable variable names is. The BNF describes a <variable> as
being any <identifier> which isn't a <syntactic keyword>, and the
<syntactic keywords> are enumerated. E.g. according to my reading of
the report, the sequence
(define block (lambda (x) (extend x 3)))
(define extend (lambda (a b) (list b a)))
(block 1)
has a perfectly well-defined meaning: BLOCK and EXTEND are variable
names (unconditionally!); these names become bound to values; the value
of BLOCK is applied to the number 1; etc. I didn't see anything in the
report which allowed any implementation to assign any other meaning to
this program fragment. Any implementation which did something different
with this code fragment (e.g., T, which has BLOCK-expressions, and
independent namespaces for variables and keywords) would not be
implementing the language described in the report.
I don't think this is a departure from the previous report, although of
course my edits have made the *description* follow my world view more
closely.
The way so-called "syntactic extensions" usually (not always) work,
however, is that they pre-empt certain identifiers for use as variable
names. E.g. an implementation might make BLOCK or EXTEND unavailable.
Or, worse, the variables remain available, but expressions whose cars
are these names are no longer treated as procedure calls. Then the
above program wouldn't have the expected meaning. I say that such
modifications to the language aren't syntactic extensions, since they
incompatibly change the meanings of programs, rather than just defining
what would otherwise be an error situation.
If the implementation is clever enough that program fragments like these
still work, i.e. the extensions are only seen when the variable is
undefined (a situation which would otherwise be an error), then that's
fine, but I don't think that's how most scheme implementations out there
actually implement their additional special form types. (Correct me if
I'm wrong. Consider forward references.)
Implementations can support macros (they can also support Algol 60 mode,
or any other incompatible change, if they want -- it's not as if it's a
sin to program in something other than reportified-scheme), so long as
there's some way to run programs written in the language described in
the report. Several existing implementations are already structured to
make it easy to support multiple such modes or incompatible dialects; so
what's the big deal?
In short: why should the report say anything at all about this issue?
To warn implementors not to do the wrong thing?
Do we want to change the report to explicitly ALLOW the preemption of
arbitrary variable names? I think Jim's question originated from a
belief that implementations were free to do this and still claim to be
adhering to the report. I think that's absurd. How should the report's
examples, much less portable programs in general, be written in that
case?
Jonathan
∂10-Jun-86 0744 @MC.LCS.MIT.EDU:dyb%indiana.csnet@CSNET-RELAY.ARPA Re: portability
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Date: Tue, 10 Jun 86 01:43:10 est
From: Kent Dybvig <dyb%indiana.csnet@CSNET-RELAY.ARPA>
To: bartley%ti-csl.csnet@CSNET-RELAY.ARPA, jar@MC.LCS.MIT.EDU
Subject: Re: portability
Cc: rrrs-authors@MC.LCS.MIT.EDU
I don't think this issue is as cut and dried as all that. Jonathan
is right on the one hand; it is ``absurd'' to write portable programs
if any identifier might be taken away by a particular implementation.
However, it is not clear to me what the most practical solution is
at this point for systems that have additional special forms or user-
defined macros. It is certainly not practical to stay away from all
special forms but those appearing in the report. Nor is it practical
to invalidate a macro when a binding is found; as Jonathan points
out, forward references become a problem. Perhaps it is practical to
complain when a binding is found; this does not allow portable code
but it does provide some level of sanity. And I'm not sure it is
practical to have a "vanilla" mode; although the issue is worthy of
consideration, what happens when someone wants a basically portable
piece of code to use a system-specific special form?
If I had to take a stand one way or another, I would probably favor
a more liberal definition of keyword---rather than saying that all
of the keywords are enumerated in the report, I would allow for the
inclusion of additional keywords by any particular implementation,
with the requirement that any implementation must provide a warning
when a keyword is used as a variable. Writing portable code would
be an iterative process, but it would be relatively painless.
But I don't really want to take a stand at this point. I would
rather leave this topic, along with the whole topic of macros, out of
the report. That way we could experiment with various ways of doing
things and at some point agree on the most practical way of dealing
with the situation.
(I was going to suggest that we require keywords to begin with an
upper-case letter so that portable code could be written by employing
only lower-case variable names, but I remembered that Scheme is case-
insensitive. Sigh...)
Kent
∂11-Jun-86 1021 @MC.LCS.MIT.EDU:TIM%upenn.csnet@CSNET-RELAY.ARPA Scheme for AI based CAI
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From: Tim Finin <Tim%upenn.csnet@CSNET-RELAY.ARPA>
Subject: Scheme for AI based CAI
To: scheme%mc.lcs.mit.edu@CSNET-RELAY.ARPA
Date: Wed, 11 Jun 86 12:59 EDT
What follows is a msg from Mark Richer via the AIED digest concerning the
use of Scheme for building AI based educational systems. I've included my
response. Others may have relevant thoughts to share with him.
Tim
--------------------------------------------------------------------------
From: Mark Richer <RICHER@SUMEX-AIM.ARPA> on Wed 11 Jun 1986 at 12:00
To: ai-ed-outgoing@SUMEX-AIM.ARPA
Subj: 1:8 Scheme; AI-ED questionnaire
AI-ED Digest Tuesday, 10 June 1986 Volume 1 : Issue 8
Today's Topics: Scheme, anyone?
AI and Education questionnaire
Date: Tue 10 Jun 86 08:29:38-PDT
From: Mark Richer <RICHER@SUMEX-AIM.ARPA>
Subject: Scheme, anyone?
I have been asked to give advice regarding the appropriateness of using
Scheme for a development effort in Intelligent Computer Assisted Instruction.
Although this is partly a research effort also, a clear goal is testing
and installing the software in high school classrooms. The hardware available
to this project is HP workstations.
Admittedly I know little about Scheme. However, my initial reaction is that
no advantages Scheme could provide over CommonLisp could offset the
disadvantages of using a language without a large user base for the
purposes of software development and installation. CommonLisp
promises to offer portability (of course there are still problems, e.g.,
graphics) and a large user community, and has other obvious advantages
because of the general acceptance of Lisp in the U.S. AI community.
I'd appreciate some feedback from people that are familiar with Scheme,
particularly if you have used it for developing a large AI-based system.
Can any argument be presented to justify the resources necessary to train
people in Scheme and build and maintain a system in this UnCommonLispLike
language? In other words, what is so special about Scheme compared to
CommonLisp?
Mark
... rest of digest deleted ...
-------------------------------------------------------------------------
From: Tim Finin <Tim@upenn> on Wed 11 Jun 1986 at 12:49
To: Mark Richer <RICHER@SUMEX-AIM>
Cc: Bonnie Webber <bonnie@upenn>, Ai Bulletin Board <scheme@upenn>
Subj: Scheme
Here are some thought on Scheme vs. CommonLisp. We use Common Lisp in our
research efforts (mostly) and Scheme as an instructional language. We are
using it in both our graduate and undergraduate programs in the core
software/programming languages courses.
Scheme is Lisp. More precisely, Scheme is what Lisp should be modulo some
software engineering arguments. I think that the biggest influence on the
development of Common Lisp was the success of Scheme as a language. The
differences between common Lisp and scheme, as programming languages, at
this point, are mostly surface level phenomina. Common Lisp does have a
much much bigger base of existing software, however.
Scheme will be the Pascal of the 90's. Scheme is fairly standardized. There
are a number of good implementations (CScheme, PC-Scheme, Chez Scheme,
MacScheme) and all ashere to the unofficial standard (The Revised Revised
Report on Scheme). I think it will be used in most of the good CS
undergraduate programs in a few years to teach basic concepts of
programming. Common Lisp, I believe, will not be used in this way. Thus,
you can expect to see an increasing "user base".
Scheme is simple. Scheme is inherently simpler and smaller than common lisp.
There is some truth to the equation of sheme/commonlisp = pascal/ada. I
think Scheme will be a beter deliverey vehicle for AIED systems. It will be
hard to sell these systems if they need an HP Bobcat or a Vaxstation to run
them. It will be easy to sell them if they run on a PC or a MAC.
I hope these thought are relevant. Tim.
∂11-Jun-86 1145 @MC.LCS.MIT.EDU:FAHLMAN@C.CS.CMU.EDU Scheme for AI based CAI
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Date: Wed, 11 Jun 1986 14:37 EDT
Message-ID: <FAHLMAN.12214016709.BABYL@C.CS.CMU.EDU>
Sender: FAHLMAN@C.CS.CMU.EDU
From: "Scott E. Fahlman" <Fahlman@C.CS.CMU.EDU>
To: Tim Finin <Tim%upenn.csnet@CSNET-RELAY.ARPA>
Cc: scheme@MC.LCS.MIT.EDU
Subject: Scheme for AI based CAI
I've been involved pretty deeply in the Common Lisp design effort for
several years. For what it's worth, I agree with most of what Tim Finin
said about Common Lisp vs. Scheme for education. Common Lisp has a lot
of ugly things in it that are there for compatibility with older Lisps,
for efficiency on certain machines, and for support of large systems.
There are a lot of features built into Common Lisp that increase the
conceptual load on the first-time user, but that are valuable for the
experienced user who has to do a big job in a hurry.
Scheme is smaller, cleaner, and more willing to break with some of the
bad ideas of the past. I would use Common Lisp for any really big job,
especially if it needs to be portable to a lot of machines. At some
point, if I were training students to go out into the world and design
intelligent systems, I'd make sure that they were exposed to Common
Lisp. But for teaching the fundamental principles of Computer Science,
Scheme provides equal or better support, with many fewer distracting
features and mis-features.
I think that students trained in Scheme would have no trouble learning
Common Lisp later, though it would be useful to warn them about the
separate function and value namespaces in Common Lisp before they get
too used to Scheme's way of doing things. And I'd try not to present
Scheme in such a way that the students will be too pure to deal with a
"dirty" language like Common Lisp when the time comes. Some of that
dirt is there for a reason, and the rest is the price we had to pay to
make Common Lisp a widely agreed-upon standard.
In the long run, I don't think that the need for a larger machine to run
Common Lisp will matter: the only real difference in resource needs is
that Common Lisp needs a couple of megabytes more than Scheme (either
real or virtual memory will do) to hold the full language, and that
difference tends to wash out once megabit memory chips start turning up
as the prize in Cracker Jacks. But for the next year or two, the choice
on the smallest machines will be between a full Scheme and a very
stripped down Common Lisp, and under those conditions Scheme wins.
I hope that Scheme won't become the Pascal of the 90's. I hate Pascal.
-- Scott Fahlman
∂13-Jun-86 0956 @MC.LCS.MIT.EDU:mmeyer%tilde%ti-csl.csnet@CSNET-RELAY.ARPA Revised↑3 Draft Comment
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Date: Fri, 13 Jun 86 10:44:00 cdt
From: Mark Meyer <mmeyer%tilde%ti-csl.csnet@CSNET-RELAY.ARPA>
To: RRRS-authors%mit-mc@CSNET-RELAY.ARPA
Subject: Revised↑3 Draft Comment
Cc: mmeyer%ti-csl.csnet@CSNET-RELAY.ARPA
In going over the grammar in the Revised↑3 Report for numbers in
Scheme, I noticed a possible omission. According to the production
<ureal R> --> <prefix R> <digit R>+ #* / <digit R>+ #* <suffix>
the production of rationals, 1/2e3 is legal syntax while 1e3/2 is not.
Shouldn't the production be amended to
<ureal R> -->
<prefix R> <digit R>+ #* <suffix> / <digit R>+ #* <suffix>
so that the numerator as well as the denominator may carry a suffix?
In that case, 1/2e3 would mean 1/2000 and 1e3/2 would be 1000/2 (=500).
Mark Meyer
(mmeyer@ti-csl)
∂15-Jun-86 1251 @MC.LCS.MIT.EDU:cth%indiana.csnet@CSNET-RELAY.ARPA Logic Continuations (Abstract)
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From: Chris Haynes <cth%indiana.csnet@CSNET-RELAY.ARPA>
To: scheme@MC.LCS.MIT.EDU
Subject: Logic Continuations (Abstract)
The following abstract of a paper, to be delivered at the Third International
Conference on Logic Programming (London, July 1986), may be of interest to the
Scheme community. The paper is also available as Indiana University Computer
Science Department Technical Report No. 183, and is to appear in The Journal
of Logic Programming in a somewhat revised from.
Logic Continuations
by Christopher Haynes
We develop a `complete' embedding of logic programming into Scheme---a
lexically scoped Lisp dialect with first-class continuations. Logic
variables are bound in the Scheme environment and the success and failure
continuations are represented as Scheme continuations. To account for the
semantics of logic variables and failure continuations, the state-space model
of control is modified in a novel way that generalizes the trail mechanism.
This assures that logic variable bindings are properly restored when
continuations are invoked to perform `lateral' control transfers that are not
possible in a traditional logic programming context. It is thereby possible
to obtain greater control over logic program behavior by using continuations
as first-class objects.
∂17-Jun-86 1621 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Number syntax
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Date: Tue 17 Jun 86 16:00:31-CDT
From: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: Number syntax
To: RRRS-Authors%mit-mc@CSNET-RELAY.ARPA
Cc: Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
Message-Id: <12215615581.31.BARTLEY@CSC60>
One irritant in the Report that we have neglected to comment on until
now (sorry!) is the syntax of numbers. We believe that Scheme numbers
are essentially equivalent to Common Lisp numbers except for the new
notion of exactness. To the extent that that is so, it seems to be a
(shudder!) ``gratuitous difference'' from Common Lisp to have an
incompatible syntax.
The R↑3RS doesn't make clear which subset of the syntax of numbers is
essential and what is optional. As implementors of systems in which
Scheme and Common Lisp must co-exist, we're faced with two potential
compatibility issues: (1) going with an ``extended subset'' of the
Report's number syntax that is compatible with Common Lisp, or (2)
going with the full number syntax in the Report to be compatible with
all other Scheme implementations.
What we'd like to see is an essential syntax for numbers which is
compatible with Common Lisp's. Additional features, including
exactness, would be optional extensions. Even so, they should not
conflict with Common Lisp. For example, the use of `#s' and the order
of <sign> and <prefix> are different in the two languages.
Our motivation, of course, is that we'd like programmers to feel free to
use either language and exchange files of data without irritating
obstacles being thrown in their path. If we can't agree on a
consistent syntax for numbers, then we'll have to provide each language
with two readers and the user will have to know which one to use.
(There are other problems, of course, such as whether `:' is a
constituent of an identifier or associated with Common Lisp package
designations. We may have to go with separate readers/modes anyway.)
Does anyone agree with us? Is there time to make such a change before
R↑3RS goes to press?
Regards,
David Bartley,
Mark Meyer
-------
∂17-Jun-86 1909 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Number syntax
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Date: Tue, 17 Jun 86 21:44:45 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: Number syntax
To: Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
cc: RRRS-Authors@MX.LCS.MIT.EDU
In-reply-to: Msg of Tue 17 Jun 86 16:00:31-CDT from David Bartley <Bartley%ti-csl.csnet at CSNET-RELAY.ARPA>
Message-ID: <[AI.AI.MIT.EDU].58406.860617.JAR>
Date: Tue 17 Jun 86 16:00:31-CDT
From: David Bartley <Bartley%ti-csl.csnet at CSNET-RELAY.ARPA>
Does anyone agree with us? Is there time to make such a change before
R↑3RS goes to press?
I agree with you, but I don't have anything at stake. If we can come to
an agreement to change, I'd be happy to make the change.
As far as time goes, I have yet to call Wexelblat again to find out the
next deadline, buI imagine it will be the first week of July (for the
September issue). I need to get a clean copy out to everyone at least,
say, 10 days before SIGPLAN's deadline, so that means we should try to
get stability by circa June 25. I'll aim for that, but of course my aim
has not been good in the past.
Jonathan
∂17-Jun-86 1912 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Policy on change-making
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Date: Tue, 17 Jun 86 22:08:58 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: Policy on change-making
To: rrrs-authors@MX.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].58425.860617.JAR>
A number of suggestions for incompatible changes are currently on the
floor. Before I start polling y'all about these various questions
(mostly removals), I would like to see if we can reach concensus on what
our policy should be for making such incompatible changes. I think the
policy we adopt will bear on the changes we decide we want to make.
Questions that should be answered:
- How radical ought we to be? That is, how important is compatibility with
last summer's report?
- Given that there will be incompatible changes, how should these be
indicated in the report? Should I clutter the main text with little
notes; should I make a list of all the changes; if I make such a list,
where should it appear --- in the "notes" section, in the introduction,
somplace else? Should the list include rationales
I guess my current bias is either to omit the list entirely or relegate
it to the notes section, in pursuit of a "crisper" [Dan Friedman's word]
document. However, I again have nothing at stake, and don't care too
much, so people with real implementations should speak up.
Changes and removals (as opposed to clarifications or extensions) so far
agreed upon include the omission of the "object table" chapter, the
omission of all the #!foo constants, and the change in meaning of
(define (foo ...) ...) [from using named-lambda to using lambda]. We
have already decided on some others, and may decide on others still, in
the coming weeks.
What other documents do: The Revised Report on Scheme has pretty
thorough notes about how the language changed, with complete rationales.
The revised Algol 60 report merely enumerates, in a footnote, the
section numbers of sections that were changed at the 1962 conference.
The Algol 68 report has a comparison with Algol 60 (3 pages) as part of
its introduction, and the Revised Algol 68 report also has a comparison
with the non-revised Algol 68 report (4 pages).
Jonathan
∂18-Jun-86 2144 @MC.LCS.MIT.EDU:dyb%indiana.csnet@CSNET-RELAY.ARPA Re: Number syntax
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From: Kent Dybvig <dyb%indiana.csnet@CSNET-RELAY.ARPA>
To: bartley%ti-csl.csnet@CSNET-RELAY.ARPA, jar@MC.LCS.MIT.EDU
Subject: Re: Number syntax
Cc: rrrs-authors@MC.LCS.MIT.EDU
I'm all for the modifications David and Mark suggest...the same issues
have been annoying me, although I have no stake in Common Lisp. I
suggest that David send out another letter with the wording/syntax he
wants to make things easier for Jonathan.
∂20-Jun-86 0202 @MC.LCS.MIT.EDU:JINX@OZ.AI.MIT.EDU Policy on change-making
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Date: 18 Jun 1986 14:33 EDT (Wed)
Message-ID: <JINX.12215850914.BABYL@MIT-OZ>
From: Bill Rozas <JINX@OZ.AI.MIT.EDU>
To: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Cc: rrrs-authors@MX.LCS.MIT.EDU
Subject: Policy on change-making
In-reply-to: Msg of 17 Jun 1986 22:08-EDT from Jonathan A Rees <JAR at AI.AI.MIT.EDU>
My feelings:
- Don't be unneccessarily radical, but fix things which are broken,
and change things to reflect the new consensus (if there is one).
- I would like the incompatibilities mentioned in the notes section.
∂23-Jun-86 1412 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Bibliography
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Date: Mon, 23 Jun 86 17:11:43 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: Bibliography
To: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].60539.860623.JAR>
I would like to update the "bibliography and references" section of
the report. If you have published new papers on Scheme-related topics
in the past year, or if you will have done so within the next few
weeks, or if you're aware of something which ought to be included,
please send me a complete, accurate reference, or an incomplete
reference and enough information for me to be able to track it down.
Already on my list of things to include are:
- Felleison et al, Reasoning with Continuations (Logic in CS conf)
- Kranz et al, ORBIT compiler (Compiler Construction conf)
- Feeley, Deux approches a l'implantation du langage Scheme (masters
thesis, Montreal)
but I'm sure there are many others.
Also, send your index entry suggestions.
Jonathan
∂26-Jun-86 2114 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Remaining questions & remarks (2)
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Date: Thu, 26 Jun 86 19:03 EDT
From: Jonathan A Rees <JAR@MIT-AI.ARPA>
Subject: Remaining questions & remarks (2)
To: rrrs-authors@MIT-MC.ARPA
Message-ID: <"860626190326.1.jar@AI"@JOE-LOUIS.LCS.MIT.EDU>
Almost no one answered my query about grandfathering. Think about it
while answering the questions below. I propose listing incompatibilites
in the "notes" section, and otherwise not worrying too much about the
incompatibilities we're introducing. I'll send out a list of known
language changes in a separate message.
Here is the second list of remaining questions and remarks. Some of
these may be duplicates.
1. BEGIN vs. SEQUENCE: this is a pretty glaring ugliness in the report;
it's obvious to the world we couldn't get consensus on this one.
Many people have told me that they don't care which one is there, so
long as there's only one. SEQUENCE was used heavily in S&ICP and
for that reason I think it should be retained; thus the options I
offer are
(a) leave things as they are (BEGIN essential with non-essential
synonym SEQUENCE),
(b) remove BEGIN and make SEQUENCE essential (noting in the Notes
section that BEGIN, like #!TRUE etc., should be supported by
those implementations which care about running code written in
the past year).
Let me know your vote if you haven't done so already.
2. Similarly but less glaringly, we have a problem with the numeric
comparisons. Again, many people have said they don't care but they only
want one set, with or without question marks. Thus I offer
the choices
(a) leave things as they are
(b) flush the alternative names <? <=? >? >=? =?
[The ones without question marks were used in S&ICP; moreover, they
exist in other Lisp dialects. The argument in favor of the ?'s is that
it allows the simple statement: "names of predicates end in question mark".]
Send me your vote.
3. REC and NAMED-LAMBDA :
Again, I sense capitulation on the part of some who have been stubborn.
The only options permitted are:
(a) Keep both
(b) Flush both
My editorial sense is that we should be able to achieve (b). Remember,
the language also doesn't have EVAL, environments, or macros, so if you
want to keep these features please say how they're different from other
"indispensible" features that the language DOESN'T have.
4. SUBSTRING-MOVE-LEFT! and SUBSTRING-MOVE-RIGHT! :
Many people have suggested removing these. Anyone who wants them
retained MUST provide a convincing rationale, for inclusion in the
report. Otherwise I'll remove them.
5. Should we say anything about the possibility of parallel or
interleaved argument evaluation? Remembering something I thought I
heard Will once say, I added the innocent little phrase "or perhaps
in parallel" to the description of procedure calling. Richard
Kelsey quickly pointed out that if it's mentioned as being a
possibly legal implementation, many otherwise valid scheme programs
may fail to run in implementations which do this, because they won't
do necessary synchronization. I agree; this is acceptable only if
we provide synchronization primitives.
6. Number input exactness: two proposals have been advanced to decide whether
a number is exact or inexact if it has no #I or #E prefix and contains no
trailing #'s.
(a) Inexact if there are digits following a decimal point, or if exponential
notation is used. Otherwise exact. (This makes exctness similar to
"floatness" in CL.)
(b) A proposal which Will advanced, which I'm unable to locate right now, so he'll
have to re-send it.
I'll additionally advance another alternative, and you can make up more of
your own:
(c) Always exact. E.g. "1.2" is exact.
7. Must a port still be a port (i.e. answer true to INPUT-PORT? or OUTPUT-PORT?)
after being closed?
8. Apparently there's no difference between ABS and MAGNITUDE. Should we
keep both? If so, should I change the presentation in any way?
9. ANGLE is what Common Lisp calls PHASE; any interest in changing the
name? ...
10. Two-argument arctangent (ATAN Y X) is unnecessary, since its effect
can be trivially achieved by (ANGLE (MAKE-RECTANGULAR X Y)). Do we
apply Occam's razor and remove it? If it's retained, then I'll just
document it as being the same as (ANGLE (MAKE-RECTANGULAR X Y)).
11. JINX says: if PROCEDURE? exists, then a portable printer can be written.
JAR replies (in jest):
(define procedure?
(lambda (obj)
(not (or (pair? obj) (null? obj) (symbol? obj) (number? obj) ...))))
Seriously however, I was the only holdout at Brandeis against having
this predicate. After thinking about this further I think it's not such
a bad idea, even though it is of limited use. Is anyone opposed to
having an essential procedure PROCEDURE?, to round out the set of type
predicates?
12. (if x 1) vs. (cond (x 1)) -- this is inconsistent, as a couple of people
have pointed out. I would expect these two expressions to have the
same meaning, but they don't. The first is defined to always return
an unspecified value. The second is defined to return the value 1
if x is true, and an unspecified value otherwise. I would like to
make this consistent, and there are two ways to do. Take your pick:
(a) Change IF expressions so that they return the value of the
second form if the first form evaluates to false.
(b) Change COND and CASE so that they return an unspecified value if
there is no ELSE clause.
Here are some arguments in favor of (a):
- It removes the possibility of inferring that an implementation might
not be tail-recursive through an alternate-less IF.
- Similarly, it makes (IF #T <exp>) mean the same as <exp>, and removes
doubt about the meaning of things like (if x (if y 1) z).
- It simplifies the macro expansion of COND as compared with (b).
- Option (b) is obviously undesirable (consider the case of mutually
exclusive test expressions in a COND).
13. Many people would like to see the (define ((((a b) c) d) e) ...)
feature go away. S&ICP doesn't use it, and it has a rather complicated
syntax (look at the BNF for evidence). Vote keep or flush.
14. Status of LOAD not resolved. If, as I suggested, LOAD is only
to be syntactically valid at top level of a file, shouldn't it be
renamed to be INCLUDE ?
15. Page breaks and tabs are mentioned in the report (actually I guess I
added them - sorry), but there are no #\PAGE or #\TAB characters.
Can this be made consistent by documenting #\PAGE and #\TAB, or
should I try to neutralize or remove the places where I mention tabs
and page breaks, by saying something to the effect that there may be
other whitespace characters, and some of these characters might
terminate comments? In Common Lisp, #\PAGE and #\TAB aren't
"standard", they're only semi-standard; and I don't believe that
16. If page breaks are documented, should the terminate comments? I think
they should (but of course they don't in Common Lisp).
17. Bartley says: "the second sentence of the description of EQUAL? should
say that EQV? is used for all objects except pairs, vectors, and
strings." Forcing it to use EQV? seems kind of random to me. This
would of course make my notion of "apparent equivalence" useless,
destroying what I deluded myself into thinking was an elegant symmetry
between EQV? and EQUAL?; maybe it's a bogus idea anyhow. I
intentionally wanted to be silent on this point, allowing EQUAL? to
return true more often than EQV? perhaps, but I don't care that much.
-----
Presentation questions:
18. Several people have complained about Clinger's perhaps overly accurate
description of what happens when variables become bound. To be
accurate, we have to say that locations are created and the initial
value is stored in the location, but this doesn't sit well with the
desire to have Scheme sound like an almost-functional language.
What to do?
19. What should the dedication be? Sussman suggested the PDP-6, which was
the world's first Lisp machine, but some people didn't like this joke.
I have changed it to Christopher Strachey in the draft.
20. Is it OK to replace "Lazy ML" with "SASL" (last paragraph of section
0.0)? This is Dan Friedman's suggestion and I approve; SASL is more
widely known. I've never heard of Lazy ML (although I can imagine what
it is).
21. Should section numbers be zero-based? I'm beginning to think this looks
unprofessional; and it just doesn't look right in several places. It
worked well in the previous version of the report, and it's clearly more
consistent with the language (which is zero-based), but it doesn't work
the way I've reorganized things. If you like zero-based section
numbers, speak up.
22. Was Scheme the first programming language to have first-class lexical
closures? Can we say anything edifying along these lines?
23. I flushed the historical note "CATCH could be provided by a procedure"
sentence (again, because two or three people thought it was random and I
agreed), but some of you have complained about this. Why should this
bit of history be present, but not others that are at least as
important?
24. CALL/CC was mentioned in a sentence in a rationale in the RRRS. I
flushed the reference because (a) a number of people find the name
CALL/CC quite distasteful and (b) it is inconsistent to mention here
that some scheme implementations provide an alternate name for this but
not also do so for LABELS, BLOCK, and a zillion other things.
25. How best to resolve the inconsistencies between terminology in text and
semantics? Namely: "I", "Ide", "identifier" in semantics vs. "variable"
in text; "Com", "command" in semantics vs. "statement" in text.
26. FORCE & DELAY are still problematic. About half of respondents said it
was better to put FORCE up front with DELAY, and the other half thought
it was fine as it was. No one gave convincing arguments.
27. Is 3.0.2 (description of procedure calls) a good place to take note that
() is not a valid procedure call?
28. In section 0.0, 2nd paragraph, before the terms "variable" and
"identifier" have been defined, it should say "variable" instead of
"identifier" to be consistent with the rest of the report. Is that OK?
29. There are two nonterminals in the BNF that need names. Currently they
are called <formals> and <formalz> which was never intended to be a
serious suggestion (I put it there to see if anyone would actually read
the BNF!). Actually one or both of these can go away if NAMED-LAMBDA
and/or (DEFINE ((( ...) ...) ...) ...) go away. Can someone who likes
these things take a look at the BNF and suggest names for these?
30. Someone wanted me to avoid discussion of immutable objects in the
discussion of operational equivalence in the 2nd paragraph before entry
for EQV? . I want to mention immutability there because I think it's
important to warn users that this might be the case, otherwise they can
easily end up writing unportable code.
-----
For your information, here are changes I've made that either don't seem
controversial or reflect what I judged to be the consensus:
Language:
Only one empty list, period. (eq? '() '()) returns true.
Kelsey asks: why does ROUND round to even? Answer: Common Lisp does it
this way. Ask Steele. Probably this has to do with statistical
niceness.
A port does not become closed as a side effect of reaching end of file.
After end of file, you'll continue to read end of file objects as long
as the port is open. It's an error to read from or write to a closed
port.
DISPLAY writes characters like WRITE-CHAR does.
-----
Presentation:
"Iterative process" --> "iterative computation" on page 3 (this change
is an example of "desussmanization").
Inserted the following sentence in section 1.0:
"In addition, \ide{+}, \ide{-}, \ide{1+}, and \ide{-1+} are identifiers."
At Dan Friedman's request, I removed Perlis from the list of authors.
Changed <? and >? to < and > in all examples.
Removed non-essential features from examples (including the big one)
where possible: (1+ x) --> (+ x 1), (-1+ x) --> (- x 1), (define (foo
...) ...) --> (define foo (lambda ...)), 1-armed if --> cond, named let
--> letrec.
Changed variable name "loop" to "recur" in the
call-with-current-continuation example.
"iff" --> "if" in section 5.1.
-----
That's all for now, folks...
Jonathan
∂27-Jun-86 0943 @MC.LCS.MIT.EDU:ramsdell%linus@mitre-bedford.ARPA r3rs presentation
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Full-Name:
Organization: The MITRE Corp., Bedford, MA
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id AA00559; Fri, 27 Jun 86 11:38:01 EDT
Posted-Date: Fri, 27 Jun 86 11:37:13 edt
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id AA19250; Fri, 27 Jun 86 11:37:13 edt
Date: Fri, 27 Jun 86 11:37:13 edt
From: ramsdell%linus@mitre-bedford.ARPA
Message-Id: <8606271537.AA19250@jymme.sun.uucp>
To: rrrs-authors%mc.lcs.mit.edu@mitre-bedford.ARPA
Subject: r3rs presentation
I went on vacation and then I had trouble getting the r3rs.tar file.
By the time I sat down to read the report, I found my Scheme mail had
grown to 100 printed pages! We have a solid group of committed people.
I would like to make a few comments on presentation. The most
important comment is about section organization. Newspaper writers
spend most of their time writing the first three paragraphs of any
article. This part of the article is often the only part read by
readers, and is important in enticing readers to continue. In the
same way, The first page is most likely to be the only page read by
many SIGPLAN readers. If I had my choice of what I would ask them to
read, it would be the material in Section 0.0, the Semantics section
that notes that scheme is lexically scoped, tail recursive, weakly
typed, ... etc. I would expand on the discussion on continutations,
as they represent one important difference between Scheme and other
languages. The Introduction, with its history of scheme, its history
of scheme reports and meetings, and acknowledgements giving names of
people that the reader will not likely know, is not that one page I
would like all to read. I suggest moving the history to the back of
the report, and use the first couple of pages to convince the reader
that the language documented in this report is worth studying.
On less significant presentation issues, I would like to present a
view that a less sophisicated user of Scheme may get about
continuations. That is, this reader may conclude that continuations
are very powerful and always expensive to use. I know that the T
compiler of 1981 generated goto's from the a catch and throw
expression that exited a loop from within a loop. (Catch and throw is
old syntax for using continuations.) Since we promise that
tail-recursive procedures are executed in constant space, can't we
promise something about certain simple uses of continuations?
Otherwise, they may avoided by programmers for the wrong reasons.
Random notes
[pg. 6, col. 2, +15] In the term "meta-program" well known?
[pg. 30, col. 1] Some note is needed explaining why there are two
different close procedures.
[pg. 29] If call-with-current-continuation calls its argument with
the current continuation, should the I/O routines call-with-input-file
and call-with-output-file be renamed call-with-input-port and
call-with-output-port?
John
∂27-Jun-86 1115 @MC.LCS.MIT.EDU:gls@Think.COM Remaining questions & remarks (2)
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Date: Fri, 27 Jun 86 13:37 EDT
From: Guy Steele <gls@Think.COM>
Subject: Remaining questions & remarks (2)
To: JAR@MIT-AI.ARPA, rrrs-authors@MIT-MC.ARPA
Cc: gls@AQUINAS
In-Reply-To: <"860626190326.1.jar@AI"@JOE-LOUIS.LCS.MIT.EDU>
Message-Id: <860627133714.3.GLS@BOETHIUS.THINK.COM>
Date: Thu, 26 Jun 86 19:03 EDT
From: Jonathan A Rees <JAR@MIT-AI.ARPA>
1. BEGIN vs. SEQUENCE: this is a pretty glaring ugliness in the report;
it's obvious to the world we couldn't get consensus on this one.
Many people have told me that they don't care which one is there, so
long as there's only one. SEQUENCE was used heavily in S&ICP and
for that reason I think it should be retained; thus the options I
offer are
(a) leave things as they are (BEGIN essential with non-essential
synonym SEQUENCE),
(b) remove BEGIN and make SEQUENCE essential (noting in the Notes
section that BEGIN, like #!TRUE etc., should be supported by
those implementations which care about running code written in
the past year).
(b)
2. Similarly but less glaringly, we have a problem with the numeric
comparisons. Again, many people have said they don't care but they only
want one set, with or without question marks. Thus I offer
the choices
(a) leave things as they are
(b) flush the alternative names <? <=? >? >=? =?
(b)
22. Was Scheme the first programming language to have first-class lexical
closures? Can we say anything edifying along these lines?
Don't forget, of course, to say that Algol 60 came real close. I think you
should research the languages GEDANKEN (Reynolds) and ISWIM (Landin), as one
of those might have had closures. I believe ISWIM was described in CACM in
the mid-1960's.
Kelsey asks: why does ROUND round to even? Answer: Common Lisp does it
this way. Ask Steele. Probably this has to do with statistical
niceness.
ROUND rounds to even because the integer "rounding modes" (floor, ceiling,
round, truncate) were chosen to correspond to the rounding modes required by
the IEEE floating point standard. That standard in turn mandates rounding
to even for what indeed amounts to statistical niceness: on the average the
effects of rounding tend to cancel out. Why round to even instead of odd?
Then further operations on those results are more likely to be exactly
representable and therefore not require further loss of accuracy due to
rounding.
--Guy
∂27-Jun-86 1653 @MC.LCS.MIT.EDU:SGR@ELEPHANT-BUTTE.SCRC.Symbolics.COM [INGRIA@G.BBN.COM: Scheme for LISPM]
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Date: Fri, 27 Jun 86 17:02 EDT
From: Stephen G. Rowley <SGR@STONY-BROOK.SCRC.Symbolics.COM>
Subject: [INGRIA@G.BBN.COM: Scheme for LISPM]
To: Scheme@MIT-MC.ARPA
Message-ID: <860627170237.3.SGR@GROUSE.SCRC.Symbolics.COM>
This sounds like a question for people on this list:
Date: Thu, 26 Jun 1986 16:47 EDT
Message-ID: <INGRIA.12217972484.BABYL@G.BBN.COM>
From: INGRIA@G.BBN.COM
To: INFO-LISPM@MC.LCS.MIT.EDU
Subject: Scheme for LISPM
Does anyone have an implementation of Scheme that runs on
LISPMs? It would be useful for us to have a version that runs on Rel6
on 36XXs. Thanks in advance.
-30-
Bob
∂27-Jun-86 1930 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU typo
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Date: Fri, 27 Jun 86 22:29 EDT
From: Jonathan A Rees <JAR@MIT-AI.ARPA>
Subject: typo
To: rrrs-authors@MIT-MC.ARPA
Message-ID: <860627222941.1.JAR@VAIL.LCS.MIT.EDU>
Of course I meant "return the value of the second form if the first
evaluates to *true*," not false.
∂27-Jun-86 2142 @MC.LCS.MIT.EDU:dfried%indiana.csnet@CSNET-RELAY.ARPA Grandfathering Responses
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Date: Fri, 27 Jun 86 11:09:20 est
From: Dan Friedman <dfried%indiana.csnet@CSNET-RELAY.ARPA>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: Grandfathering Responses
1. BEGIN vs. SEQUENCE: this is a pretty glaring ugliness in the report;
it's obvious to the world we couldn't get consensus on this one.
Many people have told me that they don't care which one is there, so
long as there's only one. SEQUENCE was used heavily in S&ICP and
for that reason I think it should be retained; thus the options I
offer are
(a) leave things as they are (BEGIN essential with non-essential
synonym SEQUENCE),
(b) remove BEGIN and make SEQUENCE essential (noting in the Notes
section that BEGIN, like #!TRUE etc., should be supported by
those implementations which care about running code written in
the past year).
Let me know your vote if you haven't done so already.
*****>> (a)
2. Similarly but less glaringly, we have a problem with the numeric
comparisons. Again, many people have said they don't care but they only
want one set, with or without question marks. Thus I offer
the choices
(a) leave things as they are
(b) flush the alternative names <? <=? >? >=? =?
[The ones without question marks were used in S&ICP; moreover, they
exist in other Lisp dialects. The argument in favor of the ?'s is that
it allows the simple statement: "names of predicates end in question mark".]
Send me your vote.
******>> (b)
3. REC and NAMED-LAMBDA :
Again, I sense capitulation on the part of some who have been stubborn.
The only options permitted are:
(a) Keep both
(b) Flush both
My editorial sense is that we should be able to achieve (b). Remember,
the language also doesn't have EVAL, environments, or macros, so if you
want to keep these features please say how they're different from other
"indispensible" features that the language DOESN'T have.
Named-lambda is totally unacceptable.
Letrec is often overkill and without macros we will be left
with using it. Rec is an incredibly powerful tool. I'd hate
to lose it from my repertoire. However, named-lambda is an
ugly so I am forced, given these choices, to opt for (b).
4. SUBSTRING-MOVE-LEFT! and SUBSTRING-MOVE-RIGHT! :
Many people have suggested removing these. Anyone who wants them
retained MUST provide a convincing rationale, for inclusion in the
report. Otherwise I'll remove them.
****>> Remove them
5. Should we say anything about the possibility of parallel or
interleaved argument evaluation? Remembering something I thought I
heard Will once say, I added the innocent little phrase "or perhaps
in parallel" to the description of procedure calling. Richard
Kelsey quickly pointed out that if it's mentioned as being a
possibly legal implementation, many otherwise valid scheme programs
may fail to run in implementations which do this, because they won't
do necessary synchronization. I agree; this is acceptable only if
we provide synchronization primitives.
****>> Yes, either provide synchonization primitives or flush the comment
8. Apparently there's no difference between ABS and MAGNITUDE. Should we
keep both? If so, should I change the presentation in any way?
*****>> don't keep both.
9. ANGLE is what Common Lisp calls PHASE; any interest in changing the
name? ...
*****>> I agree with the consensus.
10. Two-argument arctangent (ATAN Y X) is unnecessary, since its effect
can be trivially achieved by (ANGLE (MAKE-RECTANGULAR X Y)). Do we
apply Occam's razor and remove it? If it's retained, then I'll just
document it as being the same as (ANGLE (MAKE-RECTANGULAR X Y)).
*****>> follow Occam's razor here.
11. JINX says: if PROCEDURE? exists, then a portable printer can be written.
JAR replies (in jest):
(define procedure?
(lambda (obj)
(not (or (pair? obj) (null? obj) (symbol? obj) (number? obj) ...))))
Seriously however, I was the only holdout at Brandeis against having
this predicate. After thinking about this further I think it's not such
a bad idea, even though it is of limited use. Is anyone opposed to
having an essential procedure PROCEDURE?, to round out the set of type
predicates?
*****> include procedure?, but be sure that
(call/cc (lambda (k) (k (procedure? k)))) --> #t.
12. (if x 1) vs. (cond (x 1)) -- this is inconsistent, as a couple of people
have pointed out. I would expect these two expressions to have the
same meaning, but they don't. The first is defined to always return
an unspecified value. The second is defined to return the value 1
if x is true, and an unspecified value otherwise. I would like to
make this consistent, and there are two ways to do. Take your pick:
(a) Change IF expressions so that they return the value of the
second form if the first form evaluates to false.
(b) Change COND and CASE so that they return an unspecified value if
there is no ELSE clause.
Here are some arguments in favor of (a):
- It removes the possibility of inferring that an implementation might
not be tail-recursive through an alternate-less IF.
- Similarly, it makes (IF #T <exp>) mean the same as <exp>, and removes
doubt about the meaning of things like (if x (if y 1) z).
- It simplifies the macro expansion of COND as compared with (b).
- Option (b) is obviously undesirable (consider the case of mutually
exclusive test expressions in a COND).
****>> I favor including a "(when pred val) as the proper special form
for two branch-if's. That way two branch-if's would be syntactically
illegal. I've used them for about a year and I find less bugs creeping
into other's and my own programs.
13. Many people would like to see the (define ((((a b) c) d) e) ...)
feature go away. S&ICP doesn't use it, and it has a rather complicated
syntax (look at the BNF for evidence). Vote keep or flush.
*****>> flush it.
Presentation questions:
18. Several people have complained about Clinger's perhaps overly accurate
description of what happens when variables become bound. To be
accurate, we have to say that locations are created and the initial
value is stored in the location, but this doesn't sit well with the
desire to have Scheme sound like an almost-functional language.
What to do?
****> Realize that Scheme is not "almost"-functional, it's almost Algol!
I agree wholeheartedly agree with Will's characterization.
The best that can be said with respect to the functionality
of Scheme is that it contains a coherent subset that is "functional".
19. What should the dedication be? Sussman suggested the PDP-6, which was
the world's first Lisp machine, but some people didn't like this joke.
I have changed it to Christopher Strachey in the draft.
****> I prefer Christopher Strachey.
21. Should section numbers be zero-based? I'm beginning to think this looks
unprofessional; and it just doesn't look right in several places. It
worked well in the previous version of the report, and it's clearly more
consistent with the language (which is zero-based), but it doesn't work
the way I've reorganized things. If you like zero-based section
numbers, speak up.
*****> 1-based seems better.
22. Was Scheme the first programming language to have first-class lexical
closures? Can we say anything edifying along these lines?
*****> Landin's ISWIM was the first well-known one back in the early 60's.
However, I would guess that the use of "function" in the
"Lisp 1.5 Programmming Language Manual" should count as
a first-class closure. If all "lambda"'s were surrounded by
(function ...) then LISP 1.5 would model them. Furthermore,
call/cc can be written with Landin's J operat.
23. I flushed the historical note "CATCH could be provided by a procedure"
sentence (again, because two or three people thought it was random and I
agreed), but some of you have complained about this. Why should this
bit of history be present, but not others that are at least as
important?
*****> I won't argue for the history. However, the implementor who
thinks that catch (as in Common Lisp) and call/cc are the same
is in for a shock. That should perhaps be pointed out.
24. CALL/CC was mentioned in a sentence in a rationale in the RRRS. I
flushed the reference because (a) a number of people find the name
CALL/CC quite distasteful and (b) it is inconsistent to mention here
that some scheme implementations provide an alternate name for this but
not also do so for LABELS, BLOCK, and a zillion other things.
****> Carolyn Talcott in her dissertation suggested the term "note".
I could live with that. If call-with-current-continuation is
the only term, this will make those of us who write about this object
uncomfortable. I think we agreed that "call/cc" would be an
acceptable abbreviation and I would prefer to keep that name
in the report. Those who don't like the name can choose not to use it.
In a sense I agree with your argument, but "call-with-current
-continuation has 30 characters in it!, "labels" and "letrec", and
"block" and "begin" each have the same number of characters.
25. How best to resolve the inconsistencies between terminology in text and
semantics? Namely: "I", "Ide", "identifier" in semantics vs. "variable"
in text; "Com", "command" in semantics vs. "statement" in text.
****> "variable" is a "dangerous" word, try to expunge it. Opinions differ
as to what a variable is.
26. FORCE & DELAY are still problematic. About half of respondents said it
was better to put FORCE up front with DELAY, and the other half thought
it was fine as it was. No one gave convincing arguments.
****> I favor join them. I don't much care where they are joined.
28. In section 0.0, 2nd paragraph, before the terms "variable" and
"identifier" have been defined, it should say "variable" instead of
"identifier" to be consistent with the rest of the report. Is that OK?
****> See comment on 26.
29. There are two nonterminals in the BNF that need names. Currently they
are called <formals> and <formalz> which was never intended to be a
serious suggestion (I put it there to see if anyone would actually read
the BNF!). Actually one or both of these can go away if NAMED-LAMBDA
and/or (DEFINE ((( ...) ...) ...) ...) go away. Can someone who likes
these things take a look at the BNF and suggest names for these?
****> I hope they go away.
Language:
Removed non-essential features from examples (including the big one)
where possible: (1+ x) --> (+ x 1), (-1+ x) --> (- x 1), (define (foo
...) ...) --> (define foo (lambda ...)), 1-armed if --> cond, named let
--> letrec.
****> I'd still prefer "add1" or "succ" and "sub1" or "pred" to the
abuse of punnery "-1+", and its slightly weaker sibling "1+".
The cuteness of "-1+" should go. In writing for a mass audience
I have learned that there is a time and a place for clever un-pronouceable
function names. Please remove them and find pronounceable words
Dan
∂28-Jun-86 1511 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU variable vs. identifier
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Date: Sat, 28 Jun 86 12:36:57 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: variable vs. identifier
To: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].62926.860628.JAR>
From the messages I've recieved, it apparently wasn't clear why two
distinct words are needed. I want to make sure that the grammar
reflects the decision that we will leave it up to implementations
(i.e. leave it "unspecified") just what things like (let ((if ...))
...) would mean. So at the very least these expressions have to be
excluded from the grammar. Therefore one word is needed for things
that are lexically like symbols (and can appear inside of QUOTE
expressions), and another is needed for those things that can be bound
and referred to. I chose "identifier" for the first and "variable"
for the second. Thus IF is an identifier but not a variable. I like
the way this turned out, and can't think of anything else that would
work as well.
∂28-Jun-86 1511 @MC.LCS.MIT.EDU:dfried%indiana.csnet@CSNET-RELAY.ARPA Grandfathering response
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Date: Sat, 28 Jun 86 11:50:33 est
From: Dan Friedman <dfried%indiana.csnet@CSNET-RELAY.ARPA>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: Grandfathering response
1. BEGIN vs. SEQUENCE: this is a pretty glaring ugliness in the report;
it's obvious to the world we couldn't get consensus on this one.
Many people have told me that they don't care which one is there, so
long as there's only one. SEQUENCE was used heavily in S&ICP and
for that reason I think it should be retained; thus the options I
offer are
(a) leave things as they are (BEGIN essential with non-essential
synonym SEQUENCE),
(b) remove BEGIN and make SEQUENCE essential (noting in the Notes
section that BEGIN, like #!TRUE etc., should be supported by
those implementations which care about running code written in
the past year).
Let me know your vote if you haven't done so already.
*****>> (a)
2. Similarly but less glaringly, we have a problem with the numeric
comparisons. Again, many people have said they don't care but they only
want one set, with or without question marks. Thus I offer
the choices
(a) leave things as they are
(b) flush the alternative names <? <=? >? >=? =?
[The ones without question marks were used in S&ICP; moreover, they
exist in other Lisp dialects. The argument in favor of the ?'s is that
it allows the simple statement: "names of predicates end in question mark".]
Send me your vote.
******>> (b)
3. REC and NAMED-LAMBDA :
Again, I sense capitulation on the part of some who have been stubborn.
The only options permitted are:
(a) Keep both
(b) Flush both
My editorial sense is that we should be able to achieve (b). Remember,
the language also doesn't have EVAL, environments, or macros, so if you
want to keep these features please say how they're different from other
"indispensible" features that the language DOESN'T have.
Named-lambda is totally unacceptable.
Letrec is often overkill and without macros we will be left
with using it. Rec is an incredibly powerful tool. I'd hate
to lose it from my repertoire. However, named-lambda is an
ugly so I am forced, given these choices, to opt for (b).
4. SUBSTRING-MOVE-LEFT! and SUBSTRING-MOVE-RIGHT! :
Many people have suggested removing these. Anyone who wants them
retained MUST provide a convincing rationale, for inclusion in the
report. Otherwise I'll remove them.
****>> Remove them
5. Should we say anything about the possibility of parallel or
interleaved argument evaluation? Remembering something I thought I
heard Will once say, I added the innocent little phrase "or perhaps
in parallel" to the description of procedure calling. Richard
Kelsey quickly pointed out that if it's mentioned as being a
possibly legal implementation, many otherwise valid scheme programs
may fail to run in implementations which do this, because they won't
do necessary synchronization. I agree; this is acceptable only if
we provide synchronization primitives.
****>> Yes, either provide synchonization primitives or flush the comment
8. Apparently there's no difference between ABS and MAGNITUDE. Should we
keep both? If so, should I change the presentation in any way?
*****>> don't keep both.
9. ANGLE is what Common Lisp calls PHASE; any interest in changing the
name? ...
*****>> I agree with the consensus.
10. Two-argument arctangent (ATAN Y X) is unnecessary, since its effect
can be trivially achieved by (ANGLE (MAKE-RECTANGULAR X Y)). Do we
apply Occam's razor and remove it? If it's retained, then I'll just
document it as being the same as (ANGLE (MAKE-RECTANGULAR X Y)).
*****>> follow Occam's razor here.
11. JINX says: if PROCEDURE? exists, then a portable printer can be written.
JAR replies (in jest):
(define procedure?
(lambda (obj)
(not (or (pair? obj) (null? obj) (symbol? obj) (number? obj) ...))))
Seriously however, I was the only holdout at Brandeis against having
this predicate. After thinking about this further I think it's not such
a bad idea, even though it is of limited use. Is anyone opposed to
having an essential procedure PROCEDURE?, to round out the set of type
predicates?
*****> include procedure?, but be sure that
(call/cc (lambda (k) (k (procedure? k)))) --> #t.
12. (if x 1) vs. (cond (x 1)) -- this is inconsistent, as a couple of people
have pointed out. I would expect these two expressions to have the
same meaning, but they don't. The first is defined to always return
an unspecified value. The second is defined to return the value 1
if x is true, and an unspecified value otherwise. I would like to
make this consistent, and there are two ways to do. Take your pick:
(a) Change IF expressions so that they return the value of the
second form if the first form evaluates to false.
(b) Change COND and CASE so that they return an unspecified value if
there is no ELSE clause.
Here are some arguments in favor of (a):
- It removes the possibility of inferring that an implementation might
not be tail-recursive through an alternate-less IF.
- Similarly, it makes (IF #T <exp>) mean the same as <exp>, and removes
doubt about the meaning of things like (if x (if y 1) z).
- It simplifies the macro expansion of COND as compared with (b).
- Option (b) is obviously undesirable (consider the case of mutually
exclusive test expressions in a COND).
****>> I favor including a "(when pred val) as the proper special form
for two branch-if's. That way two branch-if's would be syntactically
illegal. I've used them for about a year and I find less bugs creeping
into other's and my own programs.
13. Many people would like to see the (define ((((a b) c) d) e) ...)
feature go away. S&ICP doesn't use it, and it has a rather complicated
syntax (look at the BNF for evidence). Vote keep or flush.
*****>> flush it.
Presentation questions:
18. Several people have complained about Clinger's perhaps overly accurate
description of what happens when variables become bound. To be
accurate, we have to say that locations are created and the initial
value is stored in the location, but this doesn't sit well with the
desire to have Scheme sound like an almost-functional language.
What to do?
****> Realize that Scheme is not "almost"-functional, it's almost Algol!
I agree wholeheartedly agree with Will's characterization.
The best that can be said with respect to the functionality
of Scheme is that it contains a coherent subset that is "functional".
19. What should the dedication be? Sussman suggested the PDP-6, which was
the world's first Lisp machine, but some people didn't like this joke.
I have changed it to Christopher Strachey in the draft.
****> I prefer Christopher Strachey.
21. Should section numbers be zero-based? I'm beginning to think this looks
unprofessional; and it just doesn't look right in several places. It
worked well in the previous version of the report, and it's clearly more
consistent with the language (which is zero-based), but it doesn't work
the way I've reorganized things. If you like zero-based section
numbers, speak up.
*****> 1-based seems better.
22. Was Scheme the first programming language to have first-class lexical
closures? Can we say anything edifying along these lines?
*****> Landin's ISWIM was the first well-known one back in the early 60's.
However, I would guess that the use of "function" in the
"Lisp 1.5 Programmming Language Manual" should count as
a first-class closure. If all "lambda"'s were surrounded by
(function ...) then LISP 1.5 would model them. Furthermore,
call/cc can be written with Landin's J operat.
23. I flushed the historical note "CATCH could be provided by a procedure"
sentence (again, because two or three people thought it was random and I
agreed), but some of you have complained about this. Why should this
bit of history be present, but not others that are at least as
important?
*****> I won't argue for the history. However, the implementor who
thinks that catch (as in Common Lisp) and call/cc are the same
is in for a shock. That should perhaps be pointed out.
24. CALL/CC was mentioned in a sentence in a rationale in the RRRS. I
flushed the reference because (a) a number of people find the name
CALL/CC quite distasteful and (b) it is inconsistent to mention here
that some scheme implementations provide an alternate name for this but
not also do so for LABELS, BLOCK, and a zillion other things.
****> Carolyn Talcott in her dissertation suggested the term "note".
I could live with that. If call-with-current-continuation is
the only term, this will make those of us who write about this object
uncomfortable. I think we agreed that "call/cc" would be an
acceptable abbreviation and I would prefer to keep that name
in the report. Those who don't like the name can choose not to use it.
In a sense I agree with your argument, but "call-with-current
-continuation has 30 characters in it!, "labels" and "letrec", and
"block" and "begin" each have the same number of characters.
25. How best to resolve the inconsistencies between terminology in text and
semantics? Namely: "I", "Ide", "identifier" in semantics vs. "variable"
in text; "Com", "command" in semantics vs. "statement" in text.
****> "variable" is a "dangerous" word, try to expunge it. Opinions differ
as to what a variable is.
26. FORCE & DELAY are still problematic. About half of respondents said it
was better to put FORCE up front with DELAY, and the other half thought
it was fine as it was. No one gave convincing arguments.
****> I favor join them. I don't much care where they are joined.
28. In section 0.0, 2nd paragraph, before the terms "variable" and
"identifier" have been defined, it should say "variable" instead of
"identifier" to be consistent with the rest of the report. Is that OK?
****> See comment on 26.
29. There are two nonterminals in the BNF that need names. Currently they
are called <formals> and <formalz> which was never intended to be a
serious suggestion (I put it there to see if anyone would actually read
the BNF!). Actually one or both of these can go away if NAMED-LAMBDA
and/or (DEFINE ((( ...) ...) ...) ...) go away. Can someone who likes
these things take a look at the BNF and suggest names for these?
****> I hope they go away.
Language:
Removed non-essential features from examples (including the big one)
where possible: (1+ x) --> (+ x 1), (-1+ x) --> (- x 1), (define (foo
...) ...) --> (define foo (lambda ...)), 1-armed if --> cond, named let
--> letrec.
****> I'd still prefer "add1" or "succ" and "sub1" or "pred" to the
abuse of punnery "-1+", and its slightly weaker sibling "1+".
The cuteness of "-1+" should go. In writing for a mass audience
I have learned that there is a time and a place for clever un-pronouceable
function names. Please remove them and find pronounceable words
∂29-Jun-86 1205 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU [INGRIA@G.BBN.COM: Scheme for LISPM]
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Date: Sun, 29 Jun 86 14:58:30 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: [INGRIA@G.BBN.COM: Scheme for LISPM]
To: INGRIA@BBNG.ARPA
cc: SGR@SCRC-STONY-BROOK.ARPA, Scheme@MC.LCS.MIT.EDU
In-reply-to: Msg of Fri 27 Jun 86 17:02 EDT from Stephen G. Rowley <SGR at STONY-BROOK.SCRC.Symbolics.COM>
Message-ID: <[AI.AI.MIT.EDU].63300.860629.JAR>
Date: Thu, 26 Jun 1986 16:47 EDT
Message-ID: <INGRIA.12217972484.BABYL@G.BBN.COM>
From: INGRIA@G.BBN.COM
To: INFO-LISPM@MC.LCS.MIT.EDU
Subject: Scheme for LISPM
Does anyone have an implementation of Scheme that runs on
LISPMs? It would be useful for us to have a version that runs on Rel6
on 36XXs. Thanks in advance.
I wrote one last summer. It's not great for development, since there
are no debugging facilities besides TRACE, but it works. It is written in
Common Lisp, but it has been comditionalized to make it also work in
Rel 6 Symbolics Common Lisp (which is full of bugs). If you're at BBN,
you should contact Don Allen and get a copy from him. Otherwise
contact me (JAR@MIT-AI) and I'll give you more information.
Jonathan
∂29-Jun-86 2140 @MC.LCS.MIT.EDU:dyb%indiana.csnet@CSNET-RELAY.ARPA Re: Remaining questions & remarks (2)
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Date: Sun, 29 Jun 86 19:58:16 est
From: Kent Dybvig <dyb%indiana.csnet@CSNET-RELAY.ARPA>
To: jar@MC.LCS.MIT.EDU
Subject: Re: Remaining questions & remarks (2)
Cc: rrrs-authors@MC.LCS.MIT.EDU
1. BEGIN vs. SEQUENCE: this is a pretty glaring ugliness in the report;
...
(a) leave things as they are (BEGIN essential with non-essential
...
(b) remove BEGIN and make SEQUENCE essential (noting in the Notes
...
(b) [I hate the name begin... I am always looking for a corresponding end]
2. Similarly but less glaringly, we have a problem with the numeric
...
(a) leave things as they are
(b) flush the alternative names <? <=? >? >=? =?
...
(b)
3. REC and NAMED-LAMBDA :
Again, I sense capitulation on the part of some who have been stubborn.
...
(a) Keep both
(b) Flush both
My editorial sense is that we should be able to achieve (b). Remember,
...
(b)
4. SUBSTRING-MOVE-LEFT! and SUBSTRING-MOVE-RIGHT! :
Many people have suggested removing these. Anyone who wants them
...
remove them
5. Should we say anything about the possibility of parallel or
...
remove mention of parallel argument evaluation
7. Must a port still be a port (i.e. answer true to INPUT-PORT? or OUTPUT-PORT?)
...
I would prefer if it was but not strongly
9. ANGLE is what Common Lisp calls PHASE; any interest in changing the
name? ...
call it phase
10. Two-argument arctangent (ATAN Y X) is unnecessary, since its effect
can be trivially achieved by (ANGLE (MAKE-RECTANGULAR X Y)). Do we
apply Occam's razor and remove it? If it's retained, then I'll just
document it as being the same as (ANGLE (MAKE-RECTANGULAR X Y)).
are they not different in implementations without complex numbers?
11. JINX says: if PROCEDURE? exists, then a portable printer can be written.
JAR replies (in jest):
(define procedure?
(lambda (obj)
(not (or (pair? obj) (null? obj) (symbol? obj) (number? obj) ...))))
Seriously however, I was the only holdout at Brandeis against having
...
it should be included---I would much prefer the name "closure?"
12. (if x 1) vs. (cond (x 1)) -- this is inconsistent, as a couple of people
...
(a) Change IF expressions so that they return the value of the
...
(b) Change COND and CASE so that they return an unspecified value if
...
...
(c) require if to have a consequent and include WHEN as required---this gets
rid of the whole mess and is much cleaner.
13. Many people would like to see the (define ((((a b) c) d) e) ...)
...
flush it
14. Status of LOAD not resolved. If, as I suggested, LOAD is only
...
renamed to be INCLUDE ?
no... load implies run time, include implies compile time, if they are
different
15. Page breaks and tabs are mentioned in the report (actually I guess I
...
leave them out where possible
17. Bartley says: "the second sentence of the description of EQUAL? should
...
I agree with David
Presentation questions:
18. Several people have complained about Clinger's perhaps overly accurate
...
I'd say leave Will's description.
19. What should the dedication be? Sussman suggested the PDP-6, which was
...
how about Haskell B. Curry?
20. Is it OK to replace "Lazy ML" with "SASL" (last paragraph of section
...
it does seem more appropriate; SASL predates lazy ML.
21. Should section numbers be zero-based? I'm beginning to think this looks
...
1-based seems best
22. Was Scheme the first programming language to have first-class lexical
closures? Can we say anything edifying along these lines?
ISWIM (Burge) had them about ten years prior to Scheme. might want to refer
to Burge, W.H. ``ISWIM Programming Manual,'' IBM Research Report RA129,
Yorktown Heights, New York (November 1981).
23. I flushed the historical note "CATCH could be provided by a procedure"
...
I agree, flush it.
24. CALL/CC was mentioned in a sentence in a rationale in the RRRS. I
...
definitely keep call/cc. call/cc has appeared in several papers, and it is
much easier to type in without making mistakes---the other name compromises
did not end us up with names 5 times as long
25. How best to resolve the inconsistencies between terminology in text and
semantics? Namely: "I", "Ide", "identifier" in semantics vs. "variable"
in text; "Com", "command" in semantics vs. "statement" in text.
I prefer identifier for all symbols, such as keywords and lexical identifiers,
and variable for lexical identifiers.
26. FORCE & DELAY are still problematic. About half of respondents said it
was better to put FORCE up front with DELAY, and the other half thought
it was fine as it was. No one gave convincing arguments.
they should be together, I would say where FORCE now is
27. Is 3.0.2 (description of procedure calls) a good place to take note that
() is not a valid procedure call?
it should be obvious from the syntax
28. In section 0.0, 2nd paragraph, before the terms "variable" and
"identifier" have been defined, it should say "variable" instead of
"identifier" to be consistent with the rest of the report. Is that OK?
yes
Changed variable name "loop" to "recur" in the
call-with-current-continuation example.
please don't---recur is the name of a special form in Chez Scheme and
is used by lots of people---I'd like to avoid confusion
As for grandfathering, unless the original RRRS report was distributed
much more widely than I figure it was, I would rather see no mention of
the incompatibilities. It is not worthwhile to support old features
when the affected group of people is fairly small (particularly for new
implementations). Besides, the various language manuals for existing
implementations with all their differing syntaxes were much more widely
distributed in total, and their features are not being grandfathered.
Kent
∂30-Jun-86 0741 @MC.LCS.MIT.EDU:dyb%indiana.csnet@CSNET-RELAY.ARPA Re: r3rs presentation (long)
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Date: Mon, 30 Jun 86 03:46:12 est
From: Kent Dybvig <dyb%indiana.csnet@CSNET-RELAY.ARPA>
To: ramsdell%linus@MITRE-BEDFORD.ARPA
Subject: Re: r3rs presentation (long)
Cc: rrrs-authors@MC.LCS.MIT.EDU
On less significant presentation issues, I would like to present a
view that a less sophisicated user of Scheme may get about
continuations. That is, this reader may conclude that continuations
are very powerful and always expensive to use. I know that the T
compiler of 1981 generated goto's from the a catch and throw
expression that exited a loop from within a loop. (Catch and throw is
old syntax for using continuations.) Since we promise that
tail-recursive procedures are executed in constant space, can't we
promise something about certain simple uses of continuations?
Otherwise, they may avoided by programmers for the wrong reasons.
The T compiler of 1981 did not support continuations, just Lisp-style
catch and throw. However, simple uses can be compiled into jumps or
not much more. For instance, a smart compiler can tell that
(call/cc (lambda (k) (if (zero? x) (k x) (/ 1 x))))
requires nothing more than a goto for (k x). The ability to perform
this improvement is easily lost; if k is returned, placed somewhere,
or invoked from within a closure that is returned or placed somewhere,
etc., the full continuation must be made. Recursion makes things a
little more difficult, since it requires not just a goto but some way
of recording the depth of the stack. What's more, it takes a fairly
sophisticated compiler (or some special-casing) not to trip on
(call/cc
(lambda (return)
(letrec ([g (lambda (l a)
(cond
[(null? l) a]
[else
(when (zero? (car l)) (return 'oops))
(g (cdr l) (/ a (car l)))]))])
(g some-list-of-numbers 1))))
because it appears that return is closed over even though g can be
implemented as a simple loop (but couldn't be, for example, if the
closure g itself were returned instead of 'oops). But this may be
just what the "do" expression below turns into.
(call/cc
(lambda (return)
(do ([l some-list-of-numbers (cdr l)]
[a 1 (/ a (car l))])
((null? l) a)
(when (zero? (car l)) (return 'oops)))))
(Actually, it's worse than that, since letrec is itself a derived
form and really appears as a convoluted combination of lambda and
set! expressions.)
Making a guarantee that call/cc produces essentially gotos in simple
situations might backfire, too, resulting in convoluted code to take
advantage of the faster call/cc. For instance, a programmer might
abandon map in favor of hand-coded loops, or not take full advantage
of closures and recursion.
Another problem with making such a guarantee is that call/cc is a
function, not a special form, and its value might change, e.g., for
tracing or "constraining control". Certainly, it would be possible
to generate code for the first example something like
(if (eq? call/cc *primitive-call/cc*)
{fancy goto code for (if (zero? x) (k x) (/ 1 x))}
{normal application of call/cc to (lambda (k) ...)}),
but this would be clumsy and wasteful of code space.
Some implementations of Scheme currently promote some or all primitive
functions almost to special form status... if the identifier's binding
is the expected one at compile time, assume it will be at run time and
generate inline code. For example, car and cdr might be inlined this
way. In these systems, call/cc could presumably be nailed down too.
But it cannot be guaranteed so in the RRRS without implying that some
primitives are really special forms.
Since I have brought the issue up, how does everyone feel about this
special treatment for primitives? Should it be explicitly allowed or
disallowed? All of the arguments against allowing extra special forms
come in to play here as well, plus others, so I'd say it should be
disallowed, at least by default. I have no problem with some sort of
flag controlling this behavior, e.g., (set! *benchmark-mode* #t). Or
perhaps we want to say that all primitives are special forms or that
primitive identifiers are not assignable (I don't think so).
How about making call/cc a special form? I've often wondered if it
should be even though its evaluation rule would be the same as for
function application. Call/cc is basic to any system, and support
for it must be provided by the compiler, at least in the way it
represents things. Why should something be a function and not a
special form just because its evaluation rule coincides with the
evaluation rule for function applications?
(By the way, what about "not"? How many times have you seen someone
turn a conditional expression around to avoid the extra call?)
Kent
∂01-Jul-86 1040 @MC.LCS.MIT.EDU:ramsdell%linus@mitre-bedford.ARPA Call-with-current-continuation
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From: ramsdell%linus@mitre-bedford.ARPA
Message-Id: <8607011721.AA02532@jymme.sun.uucp>
To: rrrs-authors%mc.lcs.mit.edu@mitre-bedford.ARPA
Subject: Call-with-current-continuation
I told a white lie. My worry about the way continuations are
perceived was generated from opinions expressed by a knowledgeable
computer scientist from Harvard, not by myself. This person showed a
good understanding of continuations, but worried about the runtime
overhead incurred even when continuations are used to express control
patterns that can be implemented using constant space (or a stack).
Agreeing with Kent, I cannot think of any way to promise something
about the execution of certain simple uses of continuations. I guess
we should leave the topic of how to use continuations to another
document.
We've heard reviews of r3rs from knowledgeable users of Scheme, has
anyone received an opinion of the document from a reader that is
representative of the general programming language community?
John
PS. Sorry about being sloppy about T's continuations. T of 1981
restricted continuations to those that allowed stack allocation of
control structure. You could not return from a continuation twice or
pass a continuation out of its defining environment. Thus, a more
correct statement is that CATCH and call of a T continuation was
syntax for stack-based continuations. In the interpreter, CATCH was
expanded to a lambda expression and a call to a procedure like
call-with-current-continuation, but the same restriction on the
continuations applied.
∂01-Jul-86 1432 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: Remaining questions & remarks (2)
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Date: Mon 30 Jun 86 13:47:42-CDT
From: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: Re: Remaining questions & remarks (2)
To: JAR%ai.ai.mit.edu@CSNET-RELAY.ARPA,
rrrs-authors%mc.lcs.mit.edu@CSNET-RELAY.ARPA
Cc: Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
In-Reply-To: <"860626190326.1.jar@AI"@JOE-LOUIS.LCS.MIT.EDU>
Message-Id: <12218999275.23.BARTLEY@CSC60>
=======> Here are my comments. I don't care all that much about the items
=======> I've skipped over. --David Bartley
1. BEGIN vs. SEQUENCE: this is a pretty glaring ugliness in the report
[...]
(a) leave things as they are (BEGIN essential with non-essential
synonym SEQUENCE),
(b) remove BEGIN and make SEQUENCE essential (noting in the Notes
section that BEGIN, like #!TRUE etc., should be supported by
those implementations which care about running code written in
the past year).
=======> I strongly prefer (a). BEGIN is the traditional name and is easy
=======> to understand (even without END). SEQUENCE is a *type* in Common
=======> LISP and is likely to cause confusion. I thought Hal and Gerry
=======> had indicated at Brandeis that they were willing to revise the
=======> book to use BEGIN instead of SEQUENCE. (Is my memory faulty?)
2. Similarly but less glaringly, we have a problem with the numeric
comparisons. Again, many people have said they don't care but they only
want one set, with or without question marks. Thus I offer
the choices
(a) leave things as they are
(b) flush the alternative names <? <=? >? >=? =?
=======> (b)
3. REC and NAMED-LAMBDA :
Again, I sense capitulation on the part of some who have been stubborn.
The only options permitted are:
(a) Keep both
(b) Flush both
=======> (b).
4. SUBSTRING-MOVE-LEFT! and SUBSTRING-MOVE-RIGHT! :
=======> Flush them.
5. Should we say anything about the possibility of parallel or
interleaved argument evaluation? Remembering something I thought I
heard Will once say, I added the innocent little phrase "or perhaps
in parallel" to the description of procedure calling. Richard
Kelsey quickly pointed out that if it's mentioned as being a
possibly legal implementation, many otherwise valid scheme programs
may fail to run in implementations which do this, because they won't
do necessary synchronization. I agree; this is acceptable only if
we provide synchronization primitives.
=======> Flush the reference to parallel evaluation. Keep random order
=======> evaluation.
6. Number input exactness:
=======> I haven't come to terms with exactness yet, so I don't have an
=======> opinion. Has anyone implemented this yet?
7. Must a port still be a port (i.e. answer true to INPUT-PORT? or OUTPUT-PORT?)
after being closed?
=======> Yes. (Maybe. (I don't know. (What a question!)))
8. Apparently there's no difference between ABS and MAGNITUDE. Should we
keep both? If so, should I change the presentation in any way?
=======> Flush MAGNITUDE; keep ABS.
9. ANGLE is what Common Lisp calls PHASE; any interest in changing the
name? ...
=======> Use PHASE.
10. Two-argument arctangent (ATAN Y X) is unnecessary, since its effect
can be trivially achieved by (ANGLE (MAKE-RECTANGULAR X Y)). Do we
apply Occam's razor and remove it? If it's retained, then I'll just
document it as being the same as (ANGLE (MAKE-RECTANGULAR X Y)).
=======> Is there any problem with precision here? I'll go with the
=======> consensus.
11. JINX says: if PROCEDURE? exists, then a portable printer can be written.
=======> As Dan points out, we need to make it clear whether a
=======> continuation object is a "procedure" in the sense of this
=======> predicate. If we call it CLOSURE?, as someone (Kent Dybvig?)
=======> suggested, then it should perhaps discriminate against
=======> continuations. Since it is implementation-dependent whether
=======> continuations are easily distinguished from closures, I prefer a
=======> PROCEDURE? that is true of both closures and continuations.
12. (if x 1) vs. (cond (x 1))
(a) Change IF expressions so that they return the value of the
second form if the first form evaluates to false. [TRUE]
(b) Change COND and CASE so that they return an unspecified value if
there is no ELSE clause.
=======> (a), as amended.
13. Many people would like to see the (define ((((a b) c) d) e) ...)
feature go away. S&ICP doesn't use it, and it has a rather complicated
syntax (look at the BNF for evidence). Vote keep or flush.
=======> Flush.
14. Status of LOAD not resolved. If, as I suggested, LOAD is only
to be syntactically valid at top level of a file, shouldn't it be
renamed to be INCLUDE ?
=======> I'm not sure what INCLUDE means to people. My intuition is that
=======> INCLUDE is a conditional LOAD---it is ignored if the specified
=======> files has already been loaded. LOAD is unconditional and more
=======> appropriate as a building block for smarter capabilities.
15. Page breaks and tabs are mentioned in the report (actually I guess I
added them - sorry), but there are no #\PAGE or #\TAB characters.
Can this be made consistent by documenting #\PAGE and #\TAB, or [...]
=======> Lump these under "other whitespace". I intend to treat them as
=======> in Common LISP.
16. If page breaks are documented, should the terminate comments? I think
they should (but of course they don't in Common Lisp).
=======> They won't if they are just whitespace.
17. Bartley says: "the second sentence of the description of EQUAL? should
say that EQV? is used for all objects except pairs, vectors, and
strings." Forcing it to use EQV? seems kind of random to me. This
would of course make my notion of "apparent equivalence" useless,
destroying what I deluded myself into thinking was an elegant symmetry
between EQV? and EQUAL?; maybe it's a bogus idea anyhow. I
intentionally wanted to be silent on this point, allowing EQUAL? to
return true more often than EQV? perhaps, but I don't care that much.
=======> I think that explicitly mentioning EQV? would clarify things.
=======> In particular, people want to understand how EQ?, EQV?, and
=======> EQUAL? are related. I think its easier to understand them if
=======> they monotonically become less discriminating; thus all things
=======> that are EQ? are also EQV? and EQUAL? and all things that are
=======> EQV? are also EQUAL?.
18. Several people have complained about Clinger's perhaps overly accurate
description of what happens when variables become bound. To be
accurate, we have to say that locations are created and the initial
value is stored in the location, but this doesn't sit well with the
desire to have Scheme sound like an almost-functional language.
What to do?
=======> Keep Will's description.
21. Should section numbers be zero-based? I'm beginning to think this looks
unprofessional; and it just doesn't look right in several places. It
worked well in the previous version of the report, and it's clearly more
consistent with the language (which is zero-based), but it doesn't work
the way I've reorganized things. If you like zero-based section
numbers, speak up.
=======> One-based.
23. I flushed the historical note "CATCH could be provided by a procedure"
sentence (again, because two or three people thought it was random and I
agreed), but some of you have complained about this. Why should this
bit of history be present, but not others that are at least as
important?
=======> We need to explain that CALL/CC is more than CATCH.
24. CALL/CC was mentioned in a sentence in a rationale in the RRRS. I
flushed the reference because (a) a number of people find the name
CALL/CC quite distasteful and (b) it is inconsistent to mention here
that some scheme implementations provide an alternate name for this but
not also do so for LABELS, BLOCK, and a zillion other things.
=======> Keep CALL/CC.
Language:
Only one empty list, period. (eq? '() '()) returns true.
=======> Yes.
A port does not become closed as a side effect of reaching end of file.
After end of file, you'll continue to read end of file objects as long
as the port is open. It's an error to read from or write to a closed
port.
=======> Yes. Yes. Yes.
DISPLAY writes characters like WRITE-CHAR does.
=======> Yes.
=======> Regards,
=======> David Bartley
-------
∂01-Jul-86 1446 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: Remaining questions & remarks (2)
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To: JAR@AI.AI.MIT.EDU
Cc: rrrs-authors@MC.LCS.MIT.EDU, willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
Subject: Re: Remaining questions & remarks (2)
In-Reply-To: Your message of Thu, 26 Jun 86 19:03 EDT.
<"860626190326.1.jar@AI"@JOE-LOUIS.LCS.MIT.EDU>
Date: 30 Jun 86 14:41:09 PDT (Mon)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
1. BEGIN vs. SEQUENCE...
(a) leave things as they are (BEGIN essential with non-essential
synonym SEQUENCE),
(b) remove BEGIN and make SEQUENCE essential (noting in the Notes
section that BEGIN, like #!TRUE etc., should be supported by
those implementations which care about running code written in
the past year).
*****> (a). Fix the book so we can get rid of SEQUENCE.
2. <names of arithmetic comparators>
(a) leave things as they are
(b) flush the alternative names <? <=? >? >=? =?
*****> (b). MacScheme will continue to support the alternative names.
3. REC and NAMED-LAMBDA...
(a) Keep both
(b) Flush both
*****> (b).
4. SUBSTRING-MOVE-LEFT! and SUBSTRING-MOVE-RIGHT!...
*****> Flush them, but encourage Chris Hanson to publish his suite of
operations in a separate document.
5. <the possibility of parallel or interleaved argument evaluation>
*****> Drop the comment. (I use call-without-interrupts, but that
might not be so sweet on some multiprocessors.)
6. Number input exactness: two proposals have been advanced to decide whether
a number is exact or inexact if it has no #I or #E prefix and contains no
trailing #'s.
(a) Inexact if there are digits following a decimal point, or if
exponential notation is used. Otherwise exact. (This makes
exctness similar to "floatness" in CL.)
(b) A proposal which Will advanced, which I'm unable to locate right
now, so he'll have to re-send it.
I'll additionally advance another alternative, and you can make up more of
your own:
(c) Always exact. E.g. "1.2" is exact.
*****> (b). The proposal was that exponents be treated as shorthand, so
for example 1.2e3 would be treated as though it had been written 1200,
1.2000e3 would be treated as though it had been written 1200.0, and so
on; if, after getting rid of the exponent in this way, there are
digits following a decimal point, then assume inexact; otherwise
assume exact.
(a) is also ok. I think scientists and engineers would quickly
become exasperated by (c), however.
7. Must a port still be a port...after being closed?
*****> No, but we shouldn't make a big issue of whatever we decide.
8. Apparently there's no difference between ABS and MAGNITUDE. Should we
keep both? If so, should I change the presentation in any way?
*****> Flush MAGNITUDE. Talk about ABS where MAGNITUDE is now talked
about.
9. ANGLE is what Common Lisp calls PHASE; any interest in changing the
name? ...
*****> I don't care.
10. Two-argument arctangent (ATAN Y X) is unnecessary, since its effect
can be trivially achieved by (ANGLE (MAKE-RECTANGULAR X Y)). Do we
apply Occam's razor and remove it? If it's retained, then I'll just
document it as being the same as (ANGLE (MAKE-RECTANGULAR X Y)).
*****> PLEASE don't flush two-argument ATAN, because an implementation
that supports flonums but not complexnums is going to have a hard
time with (ANGLE (MAKE-RECTANGULAR X Y)).
11. ...Is anyone opposed to having an essential procedure PROCEDURE?...
*****> I very much want one. I agree with Dan that
(call-with-current-continuation (lambda (k) (procedure? k)))
must be true.
12. (if x 1) vs. (cond (x 1)) -- this is inconsistent...
(a) Change IF expressions so that they return the value of the
second form if the first form evaluates to [true].
(b) Change COND and CASE so that they return an unspecified value if
there is no ELSE clause.
*****> (a).
13. Many people would like to see the (define ((((a b) c) d) e) ...)
feature go away.
*****> Flush. MacScheme will continue to support it.
14. Status of LOAD not resolved. If, as I suggested, LOAD is only
to be syntactically valid at top level of a file, shouldn't it be
renamed to be INCLUDE ?
*****> LOAD should be syntactically valid only at the top level of a file.
I suppose it should be renamed to INCLUDE, but I don't want to.
LOAD seems a more appropriate name for something that will in fact
be used interactively, even though we don't talk about interactive
programming in the report.
15. Page breaks and tabs are mentioned in the report (actually I guess I
added them - sorry), but there are no #\PAGE or #\TAB characters...
*****> Please neutralize the places that mention tabs and page breaks.
Let's not get hung up about characters.
16. If page breaks are documented, should [they] terminate comments?
*****> I think so.
17. Bartley says: "the second sentence of the description of EQUAL? should
say that EQV? is used for all objects except pairs, vectors, and
strings." Forcing it to use EQV? seems kind of random to me. This
would of course make my notion of "apparent equivalence" useless,
destroying what I deluded myself into thinking was an elegant symmetry
between EQV? and EQUAL?; maybe it's a bogus idea anyhow. I
intentionally wanted to be silent on this point, allowing EQUAL? to
return true more often than EQV? perhaps, but I don't care that much.
*****> I think your "apparent equivalence" was a valiant effort on behalf
of a lost cause. I think Bartley's suggestion will simplify the
report and will make the language easier to understand and use.
-----
Presentation questions:
18. Several people have complained about Clinger's perhaps overly accurate
description of what happens when variables become bound. To be
accurate, we have to say that locations are created and the initial
value is stored in the location, but this doesn't sit well with the
desire to have Scheme sound like an almost-functional language.
What to do?
*****> Admit that Scheme isn't functional. Add a note to the effect that
in programs without side effects one can safely pretend that the
variables are bound directly to the arguments.
19. What should the dedication be? Sussman suggested the PDP-6, which was
the world's first Lisp machine, but some people didn't like this joke.
I have changed it to Christopher Strachey in the draft.
*****> The abstract from the RRRS was a better joke, because it said
something serious. A dedication to DEC PDP-6 Serial Number 2
could well offend the memory of the person to whom the Algol 60
Report was dedicated, so I think we'd better flush it. Do we
have to have a dedication? I'm not sure how many of us actually
met Christopher Strachey. I remember Alonzo Church from the 1982
Lisp Conference, and he might be better; maybe we could dedicate
the report to both. I believe that Church died a couple of years
ago, but I might be thinking of Haskell Curry instead. Dan? Mitch?
20. Is it OK to replace "Lazy ML" with "SASL"...
*****> Yes.
21. Should section numbers be zero-based?
*****> I've decided that zero-based numbering is perceived as cutesy.
I've found it helpful to have an unnumbered introductory section
at the beginning of a chapter, which I think of as section 0 of
that chapter, but I think it's best not to number it that way.
My apologies for setting the precedent in the RRRS.
22. Was Scheme the first programming language to have first-class lexical
closures? Can we say anything edifying along these lines?
*****> I don't think Scheme was the first. Scheme is unique not because
it was the first to have anything (except full continuations, and
even there it was anticipated by one of Reynolds's unimplemented
languages), but because it was nearly the first at many things
and succeeded in integrating those avant garde features.
23. I flushed the historical note "CATCH could be provided by a procedure"
sentence (again, because two or three people thought it was random and I
agreed), but some of you have complained about this. Why should this
bit of history be present, but not others that are at least as
important?
*****> Something needs to be said about the evolution of the special form
into a procedure having a different name. As the paragraph stands
in the 3 June draft, it makes no connection between the operators
mentioned in the paragraph and call-with-current-continuation. The
typical reader will wonder why the paragraph is there. The reason
that history is called for in this instance is that the concepts
are completely new to most readers, and they will need help to
appreciate their significance. Someday the rationale will be
unnecessary, but by then the R3RS will be a standard reference
cited by people who want to talk about the history of
continuations.
I favor adding a sentence such as "CALL-WITH-CURRENT-CONTINUATION
is equivalent in power to the 1975 CATCH, but is a procedure rather
than a special syntax."
24. CALL/CC was mentioned in a sentence in a rationale in the RRRS. I
flushed the reference because (a) a number of people find the name
CALL/CC quite distasteful and (b) it is inconsistent to mention here
that some scheme implementations provide an alternate name for this but
not also do so for LABELS, BLOCK, and a zillion other things.
*****> As someone who writes manuals for a mass audience, I find the name
CALL/CC quite distasteful. It was in the RRRS to placate those
who objected to the length of CALL-WITH-CURRENT-CONTINUATION.
This was a political compromise; I suggest we leave the RRRS
wording alone rather than try to achieve a new compromise.
25. How best to resolve the inconsistencies between terminology in text and
semantics? Namely: "I", "Ide", "identifier" in semantics vs. "variable"
in text; "Com", "command" in semantics vs. "statement" in text.
*****> In the abstract syntax, say "identifiers (variables)" and
"commands (statements)".
26. FORCE & DELAY are still problematic...
*****> I don't care.
27. Is 3.0.2 (description of procedure calls) a good place to take note that
() is not a valid procedure call?
*****> Ok with me.
28. In section 0.0, 2nd paragraph, before the terms "variable" and
"identifier" have been defined, it should say "variable" instead of
"identifier" to be consistent with the rest of the report. Is that OK?
*****> Yes. Dan points out that the semantics of "variable" is highly
variable, but we have an advantage over most authors in that people
can turn to the formal syntax and semantics if they want to know
what's really going on. Section 2.0 is a pretty good informal
description. I think people can deal with a few loaded terms
in an overview like section 0.0.
29. There are two nonterminals in the BNF that need names. Currently they
are called <formals> and <formalz> which was never intended to be a
serious suggestion (I put it there to see if anyone would actually read
the BNF!). Actually one or both of these can go away if NAMED-LAMBDA
and/or (DEFINE ((( ...) ...) ...) ...) go away. Can someone who likes
these things take a look at the BNF and suggest names for these?
*****> I hope NAMED-LAMBDA and the complicated DEFINE syntax depart from
the report, but even if they do we still have to deal with <formalz>
in the (DEFINE (FOO . X) ...) syntax; perhaps the possibilities
could be expanded in-line.
30. Someone wanted me to avoid discussion of immutable objects in the
discussion of operational equivalence in the 2nd paragraph before entry
for EQV? . I want to mention immutability there because I think it's
important to warn users that this might be the case, otherwise they can
easily end up writing unportable code.
*****> In my opinion, the paragraph in question is too little to deal
with the problem. It uses "immutable" without explaining what
it means; worse, it appears that the typical reader is supposed
to know as a matter of course that "mutation procedures" (whatever
they are) can't be applied to immutable objects. As to which
objects are immutable, all we have is the suggestion that objects
returned by literal expressions may be immutable.
I believe the paragraph at the end of 3.0.1 is sufficient. The
report is a definition, not a tutorial.
-----
DISPLAY writes characters like WRITE-CHAR does.
*****> I assume it's ok for an implementation that represents characters as
imaginary numbers to have (DISPLAY #\a) print "-97i"?
Peace, Will
∂02-Jul-86 0515 @MC.LCS.MIT.EDU:JMILLER@OZ.AI.MIT.EDU Re: Remaining questions & remarks (2)
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Subject: Re: Remaining questions & remarks (2)
From: JMILLER@MIT-OZ
Reply-To: JMiller%OZ@MC
To: Bartley%ti-csl.csnet@CSNET-RELAY
Cc: RRRS-Authors@MC
Message-ID: <[MIT-OZ] 2-Jul-86 08:13:05.JMILLER>
In-Reply-To: <12218999275.23.BARTLEY@CSC60>
I suggest the name APPLICABLE? instead of PROCEDURE?. I
personally do not regard continuations as procedures, but I
completely understand and empathize with people on the other
side. I think the notion of applicable is a legitimate
generalization and probably would solve Bill's portable printer
problem just as well.
--Jim
∂02-Jul-86 0557 @MC.LCS.MIT.EDU:ramsdell%linus@mitre-bedford.ARPA Call-with-current-continuation
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Organization: The MITRE Corp., Bedford, MA
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Posted-Date: Wed, 2 Jul 86 08:56:47 edt
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From: ramsdell%linus@mitre-bedford.ARPA
Message-Id: <8607021256.AA03112@jymme.sun.uucp>
To: rrrs-authors%mc.lcs.mit.edu@mitre-bedford.ARPA
Subject: Call-with-current-continuation
I told a white lie. My worry about the way continuations are
perceived was generated from opinions expressed by a knowledgeable
computer scientist from Harvard, not by myself. This person showed a
good understanding of continuations, but worried about the runtime
overhead incurred even when continuations are used to express control
patterns that can be implemented using constant space (or a stack).
Agreeing with Kent, I cannot think of any way to promise something
about the execution of certain simple uses of continuations. I guess
we should leave the topic of how to use continuations to another
document.
We've heard reviews of r3rs from knowledgeable users of Scheme, has
anyone received an opinion of the document from a reader that is
representative of the general programming language community?
John
PS. Sorry about being sloppy about T's continuations. T of 1981
restricted continuations to those that allowed stack allocation of
control structure. You could not return from a continuation twice or
pass a continuation out of its defining environment. Thus, a more
correct statement is that CATCH and call of a T continuation was
syntax for stack-based continuations. In the interpreter, CATCH was
expanded to a lambda expression and a call to a procedure like
call-with-current-continuation, but the same restriction on the
continuations applied.
∂02-Jul-86 1652 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Remaining questions & remarks (2)
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Date: Wed, 2 Jul 86 19:50:46 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: Remaining questions & remarks (2)
To: JMiller@OZ.AI.MIT.EDU
cc: Bartley%ti-csl.csnet@CSNET-RELAY.ARPA,
RRRS-Authors@MC.LCS.MIT.EDU
In-reply-to: Msg of 2 Jul 1986 08:13-EDT from JMILLER at MIT-OZ
Message-ID: <[AI.AI.MIT.EDU].64955.860702.JAR>
Date: 2 Jul 1986 08:13-EDT
From: JMILLER at MIT-OZ
I suggest the name APPLICABLE? instead of PROCEDURE?. I
personally do not regard continuations as procedures, but I
completely understand and empathize with people on the other
side. I think the notion of applicable is a legitimate
generalization and probably would solve Bill's portable printer
problem just as well.
It never occurred to me that the two words could mean anything
different. Certainly whatever the name is, the predicate would return
true of all applicable things, including CAR, things created by
CALL-WITH-CURRENT-CONTINUATION, and values of LAMBDA-expressions.
If the term for this kind of object changes, then the word "procedure"
must be replaced by "applicable object" throughout the entire report. The
term "procedure," which everyone has been so careful to use so far, would
become useless for any purpose I can think of, e.g. describing the
domains of procedures. That would be unfortunate.
∂07-Jul-86 0929 @MC.LCS.MIT.EDU:VERACSD@A.ISI.EDU CL Compatiblity Package
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Date: 7 Jul 1986 12:23-EDT
Sender: VERACSD@A.ISI.EDU
Subject: CL Compatiblity Package
From: VERACSD@A.ISI.EDU
To: scheme@MC.LCS.MIT.EDU
Cc: veracsd@A.ISI.EDU
Message-ID: <[A.ISI.EDU] 7-Jul-86 12:23:31.VERACSD>
Does anyone have a CommonLisp compatiblity package for Scheme
that they are willing to share? I have developed a rudimentary
package for MacScheme, but am interested in something more
complete.
-- Cris Kobryn
∂07-Jul-86 1254 @MC.LCS.MIT.EDU:cth%indiana.csnet@CSNET-RELAY.ARPA votes and things
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Date: Mon, 7 Jul 86 12:50:06 est
From: Chris Haynes <cth%indiana.csnet@CSNET-RELAY.ARPA>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: votes and things
Cc: dfried%indiana.csnet@CSNET-RELAY.ARPA
The 3 in R↑3RALS is clever, but it looks just like a footnote
reference when the Report is cited. Such puns hurt others more than
they entertain us. How about just "Report on the Algorithmic
Language Scheme". That's different enough from all the previous
report names to avoid confusion, and brevity is a particular virtue
in things, such as titles, that are refered to repeatedly.
I strongly second John Ramsdell's comments about the introduction.
If not religated to the end, the historical material should at least
be in a seperate section following the introduction. I also agree
with him that call-with-{input,output}-PORT is better than ...-FILE
now that we have the ...-PORT? predicates.
I've used the words KEYWORD and IDENTIFIER for what Jonathan is
calling IDENTIFIER and VARIABLE, respectively. I agree with Dan that
VARIABLE is confusing, because it is often used to mean LOCATION.
But I don't feel strongly. However, it is best not to have one word
for both: if you ever mean "keyword and identifier" (or "identifier
and variable"), and not just "symbol", then say so.
My votes follow (I care most about the first and last):
1. (a) leave BEGIN alone
2. (b) flush <?, et al.
3. (b) flush REC (sigh) and NAMED-LAMBDA
4. flush SUBSTRING-MOVE-...
5. flush parallelism references, keep random order
6. (a) inexact like CL "floatness"
7. yes, objects (even ports) should never change type, or there will
be some big surprises.
8. flush MAGNITUDE
9. change ANGLE to PHASE
10. keep two-argument ATAN
11. add PROCEDURE?. For pedagogy I like to maintain a distinction
between primitives, closures (LAMBDA expression values) and reified
continuations, and I use "procedure" to refer to any applicable object.
The programmer shouldn't be able to tell the difference, so the language
should only support PROCEDURE?.
12. (c) Flush one armed IF, and replace by WHEN, as suggested by Kent
and Dan.
13. flush (define ((a b) c) ...)
14. keep LOAD as is
15. treat page breaks and tabs as whitespace, and say no more
17. EQ?, EQV? and EQUAL? should increase in strength monotonically,
as David suggested.
18. keep Clinger's accuracy wrt variables
19. Do we really need a dedication? If so, Strachey is more appropriate
than the PDP-6, Curry is better, and Church seems best.
20. SASL
21. one-based section numbering
22. Landin and Reynolds should be credited with introducing
first-class closures and continuations, but it should be emphasized
that Scheme was the first widely used language to support them and is
still the most used language that supports both.
23. note the difference between CATCH and continuations somewhere
24. CALL/CC should be listed under CALL-WITH-CURRENT-CONTINUATION as
an (optional) procedure. It should be mentioned in the following
discussion that it is an equivalent abbreviation, with no other
apology offered. Dispite objections to it by some, it is more widely
used and refered to than some other things that we have kept by way
of compromise.
Regards,
Chris Haynes
∂08-Jul-86 0538 @MC.LCS.MIT.EDU:dyb%indiana.csnet@CSNET-RELAY.ARPA display and write-char
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Date: Tue, 8 Jul 86 01:17:19 est
From: Kent Dybvig <dyb%indiana.csnet@CSNET-RELAY.ARPA>
To: jar@MC.LCS.MIT.EDU
Subject: display and write-char
Cc: rrrs-authors@MC.LCS.MIT.EDU
DISPLAY writes characters like WRITE-CHAR does.
It seems to me that this only works if the character type is
distinct from other types. I would not want display to print
an integer that happens to be a character (assuming integers
are used to represent characters) as the character value
instead of the expected sequence of numerals.
For example, if the character #\A is equivalent to the integer
65, then it seems that either
1) (write-char #\A) prints A and (display 65) prints A, or
2) (display 65) prints 65 and (write-char #\A) prints 65.
I think the original intent was that (write-char #\A) print A
and (display 65) print 65, even if #\A and 65 are the same.
Am I missing something?
Kent
∂08-Jul-86 2347 @MC.LCS.MIT.EDU:WAND%northeastern.edu@CSNET-RELAY.ARPA remaining questions & remarks (2)
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From: MITCHELL WAND <WAND%northeastern.edu@CSNET-RELAY.ARPA>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: remaining questions & remarks (2)
My comments on the "remaining questions" and a few other things:
I. I second Chris Haynes's comments on the title "R↑3RS..". It is not only
too cutesy, but also suggests an aura of impermanence: these guys are going
to keep going until....
II. Kent Dybvig should be an author, on the same basis as Kent Pitman.
Comments on the numbered issues:
1. (a) leave BEGIN essential, SEQUENCE optional.
2. (b) flush <?, etc.
3. (b) flush both REC and NAMED-LAMBDA. I feel very uneasy, however, about
the overall status of special forms, both system- and user-supplied. I will
be very unhappy if I can't have a conforming Scheme that happens to have a
REC. I suspect that this situation merely reflects our lack of understanding
of this issue.
5. Flush the possibility of parallel or interleaved argument evaluation.
7. Yes, a port must be a port forever, else what's an object for?
9. Sure, use PHASE (suppress gratuitous incompatibilities)
10. Keep 2-arg ATAN.
11. Include PROCEDURE?, and make it be true of continuations. I would also be
happy with the name APPLICABLE?, though I prefer PROCEDURE?. I strongly
oppose the name CLOSURE? .
12. (a) 2-argument IF should return the value of the 2nd arg if the first is
true. (when pred exp) is OK too.
13. Flush (define ((((a b) c) d) e) ...)
18. DEFINITELY keep Clinger's description of variable binding. It's the only
hope of sanity. As Dan pointed out, Scheme is closer to Algol than it is to a
functional language, and that's a good bit of why it's useful.
19. I vote for Chris Strachey. Church was still alive the last time I looked.
Curry was the one who died, but he had not thought much, so far as I know,
about the computational implications of his work (even though he did some
numerical analysis on the ENIAC in 1944-46, see Seldin & Hindley, "To H.B.
Curry..." 1980, p. x). I think Strachey's work, as amplified and expounded
through Scott, Stoy, Milne, etc., is a far more direct intellectual source of
our work (as expounded through Scheme) [the "our" here meaning the Scheme
community, not just me.].
20. For call-by-name, how about Algol? "This is distinct from the situation in
languages such as SASL or Algol 60, where arguments are passed by name, so
that an argument expression is not evaluated unless its value is needed by the
procedure". This sentence needs to be careful not to confuse call-by-name
with call-by-lazy or other similar things.
21. I vote for one-based section numbering. I think zero-basing is cutesy.
Also, if we are going to copy the Algol 60 typography, then sub*section
numbers should always be terminated by a period e.g.,
4.5.3.1. If statement. .... (Algol report, page 10).
23. I vote to keep the historical note about CATCH being provided by a
procedure, since Scheme IS (so far as I know) the first language to do this.
Mitch Wand
∂09-Jul-86 0340 @MC.LCS.MIT.EDU:HAL%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU mitch wand's comments
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Date: Wed, 9 Jul 1986 06:37 EDT
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From: HAL%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: mitch wand's comments
In-reply-to: Msg of 8 Jul 1986 14:43-EDT from MITCHELL WAND <WAND%northeastern.edu at CSNET-RELAY.ARPA>
I second the vote for Strachey
∂10-Jul-86 1015 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU number syntax
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Date: Thu, 10 Jul 86 12:09 EDT
From: Jonathan A Rees <JAR@MIT-AI.ARPA>
Subject: number syntax
To: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
cc: rrrs-authors@MIT-MC.ARPA
Message-ID: <860710120911.5.JAR@ROCKY-GRAZIANO.LCS.MIT.EDU>
Date: Tue 17 Jun 86 16:00:31-CDT
From: David Bartley <Bartley%ti-csl.csnet at CSNET-RELAY.ARPA>
To: RRRS-Authors%mit-mc at CSNET-RELAY.ARPA
cc: Bartley%ti-csl.csnet at CSNET-RELAY.ARPA
Re: Number syntax
Message-Id: <12215615581.31.BARTLEY@CSC60>
One irritant in the Report that we have neglected to comment on until
now (sorry!) is the syntax of numbers. We believe that Scheme numbers
are essentially equivalent to Common Lisp numbers except for the new
notion of exactness. To the extent that that is so, it seems to be a
(shudder!) ``gratuitous difference'' from Common Lisp to have an
incompatible syntax.
The R↑3RS doesn't make clear which subset of the syntax of numbers is
essential and what is optional. As implementors of systems in which
Scheme and Common Lisp must co-exist, we're faced with two potential
compatibility issues: (1) going with an ``extended subset'' of the
Report's number syntax that is compatible with Common Lisp, or (2)
going with the full number syntax in the Report to be compatible with
all other Scheme implementations.
What we'd like to see is an essential syntax for numbers which is
compatible with Common Lisp's. Additional features, including
exactness, would be optional extensions. Even so, they should not
conflict with Common Lisp. For example, the use of `#s' and the order
of <sign> and <prefix> are different in the two languages.
Our motivation, of course, is that we'd like programmers to feel free to
use either language and exchange files of data without irritating
obstacles being thrown in their path. If we can't agree on a
consistent syntax for numbers, then we'll have to provide each language
with two readers and the user will have to know which one to use.
(There are other problems, of course, such as whether `:' is a
constituent of an identifier or associated with Common Lisp package
designations. We may have to go with separate readers/modes anyway.)
Does anyone agree with us? Is there time to make such a change before
R↑3RS goes to press?
I think everyone agrees with you, and that there is time. Could you
please write a concrete proposal, preferably something close to being
suitable for inclusion in the report. Also please provide BNF. Thanks.
Jonathan
∂10-Jul-86 1016 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU call-with-*put-file --> call-with-*put-port
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Date: Thu, 10 Jul 86 13:00 EDT
From: Jonathan A Rees <JAR@MIT-AI.ARPA>
Subject: call-with-*put-file --> call-with-*put-port
To: rrrs-authors@MIT-MC.ARPA
Message-ID: <860710130002.6.JAR@ROCKY-GRAZIANO.LCS.MIT.EDU>
Date: Fri, 27 Jun 86 11:37:13 edt
From: ramsdell%linus at mitre-bedford.ARPA
To: rrrs-authors%mc.lcs.mit.edu at mitre-bedford.ARPA
Re: r3rs presentation
[pg. 29] If call-with-current-continuation calls its argument with
the current continuation, should the I/O routines call-with-input-file
and call-with-output-file be renamed call-with-input-port and
call-with-output-port?
I think this is a good idea. Does anyone object?
Jonathan
∂10-Jul-86 1228 @MC.LCS.MIT.EDU:MICHAEL@CS.COLUMBIA.EDU How big would a "minimal" scheme interpreter be?
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Date: Thu 10 Jul 86 15:22:04-EDT
From: Michael van Biema <MICHAEL@CS.COLUMBIA.EDU>
Subject: How big would a "minimal" scheme interpreter be?
To: scheme@MC.LCS.MIT.EDU
Message-ID: <12221626971.27.MICHAEL@CS.COLUMBIA.EDU>
Where minimal means just the interpreter no heap etc.
Michael
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∂10-Jul-86 1300 @MC.LCS.MIT.EDU:andy@sun3.ads.ARPA My comments on the R↑RS
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From: andy@sun3.ads.ARPA (Andy Cromarty)
To: jar%mit-mc@ads.arpa
Subject: My comments on the R↑RS
Cc: rrrs-authors%mit-mc@ads.arpa
Jonathan,
I've enclosed my comments on the R↑3RS in this note
separately from my answers to your specific questions you asked.
Hope this helps. By the way, I know that putting this all together
involves a lot of work (and sometimes a lot of refereeing), and you
should be aware that your contribution isn't going unappreciated. Thanks
for all the hard work you're putting in, and my apologies in advance
if I err here due to an insufficiently detailed reading of the report.
asc
------------------------------------------------------------------------
1. I am concerned that we have multiple conflicting goals in the
design of the document. Sometimes it is a reference manual,
and sometimes it is a technical report, and sometimes it is a
users' guide. Perhaps we must live with this if there is to
be only one report, but it might be a good idea to try to
separate out (say) the history from the reference manual parts.
This is reflected in the discussions about moving or removing
the history section, for example.
2. As you might expect, I would like to see a somewhat more vigilant
attitude in warding off the dark forces of Common Lisp. It is not
compatibilities or incompatibilities that are gratuitous; it is
the very act of being concerned with compatibility at all that is
gratuitous. We should have our own standards of what a good LISP
looks like and stick to them. The first job of a good language is
to be a good language, not to be just like another bad language
that's familiar (nor even just like another good language that's
familiar). Common Lisp's goals were nearly the opposite of
Scheme's, and however good a job the CL committee did, we owe them
no homage. I recognize that this is more an issue of the design
of Scheme than of its documentation in a report, but there seems
to me to be entirely too much concern for similarities and
dissimilarities w.r.t. Common Lisp in the report. It may be
appropriate to discuss the topic of Scheme vs. CL briefly in the
historical section, but there should be a very clear message to the
reader that CL followed Scheme -- and continues to, in the sense
that Scheme is meant to be a progressive attempt at (LISP) language
design rather than a codification and standardization of existing
ideas in prior LISPs. The CL people should be writing reports
that compare their work to ours, not the other way around. ``Let
them eat cake.'' [OK, flame off.]
3. On p.2 you list me as a Brandeis participant. Would that it were
true. I will leave to your judgement whether I should be listed
in the acknowledgements, as an author, or otherwise.
4. I agree with both your observations on the Syntax section (0.1)
-- that it makes sense to have one there and that it isn't clear
what it should say. Perhaps a fairly terse or brief description of
Scheme's simple syntax would do, e.g.
The syntax of Scheme, like that of most LISPs, provides
for great expressive power, largely due to its simplicity.
An important consequence of this simplicity is the
susceptibility of Scheme programs and data to uniform
treatment by other Scheme programs. As with other LISPs,
the ``read'' function actually parses its input; that is, it
performs syntactic as well as lexical decomposition of what
it reads, rendering input in a uniform internal representation
and making it particularly easy to manipulate Scheme programs
and data in a correspondingly direct and uniform fashion.
Scheme employs a parenthesized-list Polish notation to
describe programs and (other) data, with lists recursively
defined as being composed of lists and what are
sometimes referred to as ``atomic'' objects (numbers,
symbols, etc.) \foot{Unlike most LISPs, Scheme does not
explicitly provide a predicate for assessing atomicity,
although it does contain predicates for determining whether an
object is a list, symbol, number, etc.} The syntax of Scheme
expressions is described formally in greater detail later in
this report.
5. Identifiers & keywords: Sections 1.0 and 2.0 gave me pause,
because I have been concerned for some time with the keyword
problem in Scheme (and I admit to being dissatisfied with the
most common solution). The statement
``Any identifier which is not a syntactic keyword may be
used as a variable....''
which appears in both sections implies that there are keywords in
the language, although (a) there aren't guaranteed to be and (b)
you haven't said anything previously about keywords in the
document. The astute reader will then turn to the index to find
out what she has missed, only to discover that there is no entry
at all for keywords. Later on there is a discussion of keywords,
but it is essentially an afterthought, and by now the reader may
have decided that Scheme really is Pascal after all (Andrew, bite
your tongue). Something needs to be done to clear up the
potential confusion from the initial presentation of identifiers
vs. keywords. The inline "Note:" on p.6 probably does not serve
to clarify things as much as it might.
6. P. 6, SS 2.0: Yes, mention that there are no guarantees that a
``top-level'' exists. (Then encourage the rest of the RRRRS
authors read that paragraph....)
7. SS 2.1, p.6 implies that there are other values besides #f that
count as false. Except for the optional #!false, I'm not sure I
see what these are. Perhaps you count things like (NOT #T) as
false for the purposes of this section?
8. p. 7, SS3.0.2 -- Typo at bottom of page, ``combinations. .''
9. p.7 SS 3.0.2: It may not be clear to non-LISPophiles what
``+`` evals to, or why ``+'' gets evaluated in the example
(+ 3 4) => 7
((if #f + *) 3 4) => 12
The idea of a function name evaluating to a functional object
will not be intuitive for most readers, who probably think in
languages that don't have first-class procedures. Perhaps
something can be done to make this clearer.
10. There are a few minor report points that reflect major
underlying problems we really have yet to solve in the design
of Scheme, involving things like COND, IF, and perhaps LET. The
syntax definitions provided earlier on in the report make (COND ((X)))
a legal expression, and we've already had the n-armed IF argument.
Similarly, (LET () (DOSOMETHING)) is legal, although perverse and
not obviously useful. (The latter expression actually appears in
the report, at the top of p.10 col2, although I can see no reason
to have used it -- the example would have worked fine without it.)
I think what has happened is that we never resolved the issue of
``functions'' that don't return values. Instead we developed, or
permitted the random evolution of, a hodgepodge of mutually
inconsistent local solutions: DEFINE is not an expression, IF may
(or may not) have an undefined return value, (COND ((X))) returns
(X), etc. We still have design work to do.
11. On a related syntax (or is it design?) point, on p.9, SS3.1.0, the
expression (CASE TEST (() (FOO))) is permitted. It's not clear to me
why we want to permit this, nor what it means if we do. Strictly,
it would always be ignored, in which case it's spurious.
Similarly, (CASE TEST) is legal; strictly it returns <unspecified>
but seems senseless nonetheless.
12. I cannot refrain from observing that DO is truly ugly, a
veritable pig of a construct, and we could have done better.
We are indeed fortunate that its use under practical circumstances
is rarely necessary.
13. The Note: on p.11 about DO in which you describe assignment vs.
rebinding is guaranteed to be lost on the majority of readers.
An example of how it differs from other LISPs' DO might help.
14. On p.12 where QUASIQUOTE is introduced, as a purely typographic
observation, we really need a better backquote character. It's
very hard to read the character at all in the copy of the report
I have, especially at that point size. At first glance I thought
in all honesty that it was a speck of ink on my copy. (I believe
my hardcopy came from MIT, although its route was sufficiently
mysterious that it might have been printed at Berkeley instead.)
15. SS 4.0 talk about the ``top level,'' as if there is one; cf. my
point #6 above.
16. SS 4.1, p.12, first sentence: I find this ambiguous:
Definitions are not valid in all contexts where expressions
are allowed; they are only valid at the top level [sic] of
a <program> and at the beginning of a lambda body.
This could mean any of several things, e.g.:
Definitions are invalid in all contexts where expressions are
allowed (i.e. there are no contexts in which definitions are
valid where expressions are allowed)....
or
Definitions are invalid in some contexts where expressions
are allowed (i.e. there exist contexts where expressions are
allowed but wherein definitions are not allowed)....
This probably needs to be rephrased for people who don't already
know what it's trying to say.
17. Top of p.13 col1: You have ``(. <variable>) would be understood
to mean simply <variable>.'' Why permit this? It offers no
additional functionality and strikes me as an unclean misfeature.
18. p.14, SS 5.1: Misspelling, ``distint'' => ``distinct''.
19. p.17, SS5.2: Misspelling, ``decsription'' => ``description''.
20. Predicates: As far as I could see, we never actually commit to
putting ``?'' at the end of predicates, although we do
mention on p.18 that functions like ASSV don't end in ``?''
because they aren't predicates. This convention would be a good
thing to assert. (It also would blow the people who dislike >?
out of the water, I'm afraid.)
21. p. 18, SS 5.3, First sentence: ``entirely'' is massive
overstatement here. There are lots of bases for the utility of
symbols -- like their use as printable undoublequoted objects, which
seems to me to have been lost almost entirely [sic] on the
Scheme community (hence the rejection of upper/lower case
distinction). (Incidentally, CommonLisp also gets control of
UC/LC terribly wrong, to my eternal annoyance when I build
distributed multiprocessing mostly-LISP-based systems that want
to communicate by passing case-varying symbol tokens instead of
strings.)
22. p.28, SS 5.8: What happened to TeX in the middle of column 2
where it says ``The escape procedure''? Misplaced manual
linebreak, perhaps.
23. NOTES, p.35ff.: This material should stay somehow. We need to
make it clear that R↑3 Scheme is not being touted as Yet Another
Ultimate Solution To The Programming Language Problem, but rather
as a snapshot of a *process* of good design, for which not all
answers have yet been found. We also ought to use the opportunity
for publicity afforded us by SIGPLAN to advertise some of the thorny
unsolved problems that need further research, and encourage
language designers to work on them.
-------------------------------------------------------------------------
∂10-Jul-86 1313 @MC.LCS.MIT.EDU:MICHAEL@CS.COLUMBIA.EDU [Michael van Biema <MICHAEL@CS.COLUMBIA.EDU>: How big would a "minimal" scheme interpreter be?]
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Subject: [Michael van Biema <MICHAEL@CS.COLUMBIA.EDU>: How big would a "minimal" scheme interpreter be?]
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From: Michael van Biema <MICHAEL@CS.COLUMBIA.EDU>
Subject: How big would a "minimal" scheme interpreter be?
To: scheme@MC.LCS.MIT.EDU
Message-ID: <12221626971.27.MICHAEL@CS.COLUMBIA.EDU>
Where minimal means just the interpreter no heap etc.
Michael
-------
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∂10-Jul-86 1342 @MC.LCS.MIT.EDU:wagle%iuvax.indiana.edu@CSNET-RELAY.ARPA Re: Remaining questions & remarks (2)
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From: Perry Wagle <wagle%iuvax.indiana.edu@CSNET-RELAY.ARPA>
To: rrrs-authors%mit-mc.CSNET@CSNET-RELAY.ARPA
Subject: Re: Remaining questions & remarks (2)
Cc: wagle%iuvax.indiana.edu@CSNET-RELAY.ARPA
(2) <, >, etc are composed solely of "special symbols", and classically are
predicates. With this view in mind, perhaps the exception is not so big
as naive application of Occam's Razor would suggest. I support essential
<, >, etc, and the removal of their "xxx?" counterparts.
(5) Many otherwise portable Scheme programs would die under unrestrained
interleaving. I claim that a Scheme should have the semantics of a
single logical processor no matter what the underlying architecture is.
I think that mention of parallelism should be left out altogether, as
any mention would call for ad hoc measures (synchronization primitives?
bleagh!), and restraint to a "single logical processor" is probably an
obituary (within ten years or so?).
(7) I would like to guard input and output commands with INPUT-PORT? and
OUTPUT-PORT? respectively. I think closed ports SHOULD be ports, but
not input or output ports; I support the predicate: PORT?.
(11) I would very much like PROCEDURE? and consider continuation objects
to be procedures. While appealing, I don't support APPLICABLE? as it
would be the only type predicate that doesn't name the type its checking
for.
(12) I oppose one-armed IFs. I've been happy with WHEN and UNLESS that
return NIL when the condition isn't met.
(14) I have "meta"-procedures that invoke LOAD. I *demand* that you not cut
my arms and legs off for "esthetic reasons".
(15) I think that *all* ASCII characters should be "legibly typable" (e.g.
#\null, etc), but then I only run on ASCII machines.
∂10-Jul-86 1540 @MC.LCS.MIT.EDU:andy@sun3.ads.ARPA My answers to your thirty questions on R↑RS
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From: andy@sun3.ads.ARPA (Andy Cromarty)
To: jar%mit-mc@ads.arpa
Subject: My answers to your thirty questions on R↑RS
Cc: rrrs-authors%mit-mc@ads.arpa
Jonathan,
Here is my list of answers to the specific report-related questions
you posed to the group. I've only answered the ones I have strong
opinion on.
1. The presence of BEGIN in Scheme is frankly somewhat of an
embarrasment. It really should be flushed, but politically
it's probably too late. Still, I vote (b).
2. Keep the >? forms. All predicates should end in ? for
uniformity. This kind of consistency is much more important for
pedagogical purposes than is similarity to CL, Pascal, or any
other existing language.
4. Substring-move-*: flush. I think I have simple Scheme definitions
for these, if anyone needs them once they're flushed.
5. Simply make it clear that evaluation order is unspecified (and
should not be depended on); to guarantee sequential evaluation
of a collection of combinations, use SEQUENCE.
7. Port = port. Safer that way.
11. Yes, PROCEDURE? would be welcome.
12. (if x 1) vs. (cond ((x 1)): I suggest
(if x 1) => 1 iff x, else <unspecified>
(cond ((x 1))) => 1 iff x, else <unspecified>
(case (not (not x)) ((#t) 1)) => 1 iff x, else <unspecified>
This follows the general principle that if you fall off the end
of a control construct, the results are not guaranteed. If you
want a guaranteed return value in your program, you specify one
using ELSE or the two-armed IF as appropriate; that's what they're
there for. This should be phrased to say that ``it is an error''
to rely on the result of a control construct that returns an
<unspecified> result.
13. Flush (define ((((a b) c) d) e) ...) syntax.
14. To me, INCLUDE means "include." If we want the effect to be
equivalent to having the loaded text be lexically present,
INCLUDE is an excellent name, and helps avoid some of the
concerns people have had about what it means to have a dynamic
programming environment for a lexically scoped language. I would,
however, want to see a resolution to such problems as
(IF X (INCLUDE "FOO"))
If this evaluation depends on the dynamics of the binding
environment, then "LOAD" is more appropriate. INCLUDE would
have to be a non-expression statement, e.g. the above example
would only be syntactically correct if "FOO" happened to contain
exactly one or two expressions at the top level of the file, and
the INCLUDE would always get performed regardless of X's value.
21. One-based sections.
24. I guess some people don't like to type and have bad editors, or
maybe bad pretty-printers. CALL/CC is scarcely an intuitive
name; its chief virtue seems to be the number of characters it
contains. But it seems to be regionally entrenched; keep it
"informally optional" to the standard CALL-WITH-CURRENT-CONTINUATION
if necessary. (It will not appear in our Scheme implementations.)
26. FORCE and DELAY are new ideas to most readers of the report, at
least for its SIGPLAN incarnation. Good pedagogy suggests they
be put together if possible.
27. Yes for () in 3.0.2.
30. I thought the question of immutable objects was lightly treated
overall. Rather than remove the reference on p. 14 SS 5.1, I'd
prefer to see more detail, and perhaps (a) something explicitly
noting that set-car! and set-cdr! are destructors (or
mutators if you prefer) and (b) the explicit assertion that
destructors end in ``!'' in Scheme.
------------------------------------------------------------------------
Other topics:
-1+ : I prefer to see this kept, in inessential status. When I first
saw it, it struck me as the first time any LISP had gotten this
right. It says exactly what it means. Better no decrement
function at all, however, than using "1-" to mean decrement; "1-"
says exaactly what it *doesn't* mean.
Since there was a complaint, I might suggest ``minus one plus''
as the pronunciation for "-1+", as in "minus one plus 3" for
(-1+ 3) (or "negative one plus three," if you prefer). I
scarcely find SUCC pronounceable in any socially acceptable way,
and it certainly doesn't seem to me to be a serious alternative.
WHEN: This probably seems like a good idea to people who don't do
concurrent programming. When you deal with time in your
programs, ``when'' already has a confusing enough meaning without
overloading it to mean IF. For that matter, a couple years from
now we may want to use WHEN for event management.
S&ICP: I do not know what it means to (as one person admonished)
``fix the book''; in particular, I don't know how you recall
thousands of copies. Independent of the quality of the
presentation and choices reflected in S&ICP, which I admit to
admiring tremendously, I believe that this book has done
more for Scheme than any other single force in Scheme's history,
and I believe we should endeavor to support a Scheme compatible
with it. Most of my colleages who own the book have it because
they were interested in obtaining a good book on LISP or a good
book on programming, and to a person every one with whom I've
spoken agrees that it is probably the best available for both
purposes. Let's not kill the goose that lays our golden eggs.
∂10-Jul-86 1941 @MC.LCS.MIT.EDU:whill%hplabsc@hplabs.HP.COM Re: [Michael van Biema <MICHAEL@CS.COLUMBIA.EDU>: How big would a "minimal" scheme interpreter be?]
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Date: Thu, 10 Jul 86 19:33:39 pdt
From: Walt Hill <whill%hplabsc@hplabs.HP.COM>
Message-Id: <8607110233.AA15511@hplabsc>
To: MICHAEL@CS.COLUMBIA.EDU, scheme@MC.LCS.MIT.EDU
Subject: Re: [Michael van Biema <MICHAEL@CS.COLUMBIA.EDU>: How big would a "minimal" scheme interpreter be?]
MIT CScheme will run on an HP Integral PC with 1.5Meg RAM with room for only
40K items in the heap.
Walt Hill
∂11-Jul-86 0336 @MC.LCS.MIT.EDU:bc@MEDIA-LAB.MIT.EDU MacScheme
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From: William H Coderre <bc@MEDIA-LAB.MIT.EDU>
Message-Id: <8607111031.AA06695@MEDIA-LAB.MIT.EDU>
To: scheme@mc.lcs.mit.edu
Subject: MacScheme
Can someone summarize the MacScheme situation?
I've played briefly with a fairly old version.
I heard there was a new version.
Graphics? Toolbox? Editor (I remember it being a loser)?
Compatibility?
Thank You
"Tzima Narki"......................,...........,.............bc
∂11-Jul-86 0925 @MC.LCS.MIT.EDU:gls@Think.COM My comments on the R↑RS
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Date: Fri, 11 Jul 86 12:19 EDT
From: Guy Steele <gls@Think.COM>
Subject: My comments on the R↑RS
To: andy@sun3.ads.ARPA, jar%mit-mc@ads.ARPA
Cc: rrrs-authors%mit-mc@ads.ARPA, gls@AQUINAS.ARPA
In-Reply-To: <8607101959.AA12928@Zarathustra.Think.COM>
Message-Id: <860711121914.1.GLS@BOTOLPH.THINK.COM>
Date: Thu, 10 Jul 86 12:39:26 PDT
From: andy@sun3.ads.ARPA (Andy Cromarty)
Jonathan,
I've enclosed my comments on the R↑3RS in this note
separately from my answers to your specific questions you asked.
Hope this helps. By the way, I know that putting this all together
involves a lot of work (and sometimes a lot of refereeing), and you
should be aware that your contribution isn't going unappreciated. Thanks
for all the hard work you're putting in, and my apologies in advance
if I err here due to an insufficiently detailed reading of the report.
Hear, hear!
...
2. As you might expect, I would like to see a somewhat more vigilant
attitude in warding off the dark forces of Common Lisp. It is not
compatibilities or incompatibilities that are gratuitous; it is
the very act of being concerned with compatibility at all that is
gratuitous. We should have our own standards of what a good LISP
looks like and stick to them. The first job of a good language is
to be a good language, not to be just like another bad language
that's familiar (nor even just like another good language that's
familiar). Common Lisp's goals were nearly the opposite of
Scheme's, and however good a job the CL committee did, we owe them
no homage. I recognize that this is more an issue of the design
of Scheme than of its documentation in a report, but there seems
to me to be entirely too much concern for similarities and
dissimilarities w.r.t. Common Lisp in the report. It may be
appropriate to discuss the topic of Scheme vs. CL briefly in the
historical section, but there should be a very clear message to the
reader that CL followed Scheme -- and continues to, in the sense
that Scheme is meant to be a progressive attempt at (LISP) language
design rather than a codification and standardization of existing
ideas in prior LISPs. The CL people should be writing reports
that compare their work to ours, not the other way around. ``Let
them eat cake.'' [OK, flame off.]
[a] I think that many papers on Common Lisp have correctly attributed its
debt to Scheme.
[b] I disagree that concern with compatibility is gratuitous. Perhaps that
concern should be subordinate to other concerns, but when everything else is
truly equal then compatibility is a reasonable criterion for breaking ties.
This is because it is better to be able to tie a feature to something already
familiar than to make a user learn something new.
[c] There should be a very clear message to the reader that Scheme certainly
does owe debts to other sources, and one of them is Common Lisp. While
Scheme certainly has been the pioneer in the treatment of closures and
functional programming in a Lisp framework, I think it is fair to say that
Common lisp pioneered a rational (forgive the pun) treatment of numeric data
types in a Lisp framework, and my impression is that Scheme learned
something in this area from the Common Lisp experience.
[d] Don't forget that there are some people who worked on both Scheme and
Common Lisp at the same time (I do not count myself as one, by the way), to
whom I am grateful because they learned certain lessons in both contexts at
once and served to transfer ideas in both directions.
12. I cannot refrain from observing that DO is truly ugly, a
veritable pig of a construct, and we could have done better.
We are indeed fortunate that its use under practical circumstances
is rarely necessary.
I strongly disagree. DO is a construct that emphasizes the notion that
an iteration can proceed by initializing some state variables and then
repeatedly transforming them while maintaining some invariant until
a condition is reached. In particular, it emphasizes the fact that
outputs of the iteration as well as inputs can and should be expressed
as iterator-controlled variables. This is a lesson that the "algebraic"
languages ought to learn. It is an abomination to see
sum = 0
do i = 1 to 10 by 1
sum = sum + a(i)
end do
instead of
do i = 1 to 10 by 1; sum = 0 by a(i); result sum od
23. NOTES, p.35ff.: This material should stay somehow. We need to
make it clear that R↑3 Scheme is not being touted as Yet Another
Ultimate Solution To The Programming Language Problem, but rather
as a snapshot of a *process* of good design, for which not all
answers have yet been found. We also ought to use the opportunity
for publicity afforded us by SIGPLAN to advertise some of the thorny
unsolved problems that need further research, and encourage
language designers to work on them.
Yes.
--Guy
∂11-Jul-86 0935 @MC.LCS.MIT.EDU:cscott@bfly-vax.bbn.com tiny scheme
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Date: Fri, 11 Jul 86 12:22:23 EDT
From: "Curtis A. Scott" <cscott@bfly-vax.bbn.com>
To: michael@cs.columbia.edu
cc: scheme@mc.lcs.mit.edu
Subject: tiny scheme
It depends on the level of functionality you desire. A minimal kernel
with only the basic operations as primitives could be very small. I
wrote a student subset kernel in Z80 assembler which was much less
than 32K bytes, and I believe someone did one for the Apple II of
similar size. You have then moved much of the size of the system off
into interpreted code in the heap. None of the "real" systems are
this small; the MIT handcoded 68000 scheme was around 64K of code.
∂11-Jul-86 1142 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: My comments on the R↑RS
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Date: Fri 11 Jul 86 10:59:37-CDT
From: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: Re: My comments on the R↑RS
To: andy%sun3.ads@CSNET-RELAY.ARPA, jar%mit-mc%ads@CSNET-RELAY.ARPA
Cc: rrrs-authors%mit-mc%ads@CSNET-RELAY.ARPA,
Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
In-Reply-To: Message from "Andy Cromarty <andy@sun3.ads.ARPA>" of Fri 11 Jul 86 04:08:40-CDT
Message-Id: <12221852261.67.BARTLEY@CSC60>
>Date: Thu, 10 Jul 86 12:39:26 PDT
>From: Andy Cromarty <andy@sun3.ads.ARPA>
> [...]
>2. As you might expect, I would like to see a somewhat more vigilant
> attitude in warding off the dark forces of Common Lisp. It is not
> compatibilities or incompatibilities that are gratuitous; it is
> the very act of being concerned with compatibility at all that is
> gratuitous. ...
I feel that this point of view is not in Scheme's best interest. Although
many potential converts to Scheme are unsullied by contact with lesser
lisps, others must either be won away from Common Lisp or must live with
both. Gratuitous differences in syntax and in the naming of standard
procedures make it much more difficult for them to give Scheme a fair
trial. Also, many of us are working on implementations in which Scheme
and Common Lisp programs want to share data and call each other.
Gratuitous differences in the data types and in the syntax of numbers (for
example) can make this very frustrating. I fear that Scheme will usually
be the one that loses if a development team decides the two languages are
not sufficiently compatible.
> ... We should have our own standards of what a good LISP
> looks like and stick to them. The first job of a good language is
> to be a good language, not to be just like another bad language
> that's familiar (nor even just like another good language that's
> familiar). Common Lisp's goals were nearly the opposite of
> Scheme's, and however good a job the CL committee did, we owe them
> no homage. ...
Although a certain amount of compromise is necessary in agreeing on what
is "gratuitous", it certainly is true that any compromise that changed
Scheme from a "good" language to a "bad" one would not be gratuitous.
> ... I recognize that this is more an issue of the design
> of Scheme than of its documentation in a report, but there seems
> to me to be entirely too much concern for similarities and
> dissimilarities w.r.t. Common Lisp in the report. It may be
> appropriate to discuss the topic of Scheme vs. CL briefly in the
> historical section, but there should be a very clear message to the
> reader that CL followed Scheme -- and continues to, in the sense
> that Scheme is meant to be a progressive attempt at (LISP) language
> design rather than a codification and standardization of existing
> ideas in prior LISPs. The CL people should be writing reports
> that compare their work to ours, not the other way around. ``Let
> them eat cake.'' [OK, flame off.]
I think we've all agreed that explicit references to Common Lisp in the
Report should be minimized.
Regards,
David Bartley
-------
∂11-Jul-86 1642 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU test
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Date: Fri, 11 Jul 86 18:04:44 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: test
To: scheme@MC.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].68642.860711.JAR>
Test message. Please ignore.
∂12-Jul-86 1837 @MC.LCS.MIT.EDU:RPG@SU-AI.ARPA Compatibility with Common Lisp: A meta comment
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Date: 12 Jul 86 1835 PDT
From: Dick Gabriel <RPG@SU-AI.ARPA>
Subject: Compatibility with Common Lisp: A meta comment
To: rrrs-authors@MC.LCS.MIT.EDU
Andy Cromarty comments that it is ``the very act of being concerned with
compatibility at all that is gratuitous.''
I regard it as lucky that this message only went to RRRS-authors, because
it represents a low point in political thinking. Although I am not an
active participant in the Scheme design, many of you know that I use
Scheme in my teaching, my research papers, and my research. When put on
the spot regarding the future of Lisp - in any forum - I point to Scheme
as the hope for the future.
However, I regard myself as a member of the Common Lisp community, and I
had a fair amount to do with its design and acceptance. When I read Andy's
message I felt insulted. Perhaps someone less sympathetic to the Scheme
movement would be completely turned away from Scheme by reading his
message.
If Andy wants to battle the dark forces, they are indeed lined up at the
perimeter. To the vast audience, Common Lisp and Scheme are
indistinguishable. The alternative is C. If Lisp cannot make a go of it
because other languages are seen as `better,' there will be less interest
in learning Lisp, and fewer people will be able to see the beauty of
Scheme. The battle is to win people over to `lisp programming,' which in
its best clothes is Scheme programming.
To an outsider, a `gratuitious' difference between Common Lisp and Scheme
is seen as evidence that the Lisp world is too religious to understand
real-world concerns. Unless there is a compelling reason to vary from Common
Lisp, I think compatibility is wise.
The Common Lisp community has learned and is learning a lot about how
people are won over to a new standard, and this community has many members
who are Scheme lovers. Perhaps it is a smart move to avoid alienating
them with comments like Andy's? Perhaps the Scheme community would like to
enlist the aid of the large Common Lisp community in advocating Scheme?
Don't let anyone outside this list see Andy's message.
-rpg-
ps. To be a pissant about it. I guess Andy feels that, because the goals of
Common Lisp were nearly the opposite of Scheme's, the goals of Scheme
are to be:
non-common
non-portable
inconsistent
inexpressive
incompatible
inefficient
not powerful
unstable
Common Lisp's goals were not bad. They were the stated ones, plus several
others: gain support among competing dialects, gain advocates from the
commercial Lisp programming world, and develop compromises among enemies. The
stated goals plus these three are such that we are lucky that the result
is as reasonable as it is.
∂13-Jul-86 1528 @MC.LCS.MIT.EDU:andy@sun3.ads.ARPA Scheme's DO construct
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Date: Sat, 12 Jul 86 19:07:07 PDT
From: andy@sun3.ads.ARPA (Andy Cromarty)
To: rrrs-authors%mit-mc@ads.arpa
Subject: Scheme's DO construct
Cc: andy@ads.arpa, gls%think@ads.arpa
Reply-To: andy@ADS.arpa
Hmm, I seem to have generated some controversy. I'll attempt to
provide clarifications and responses separately on each topic to
help keep the discussions distinct. I'll start with "DO."
------------------------------------------------------------------------
I cannot refrain from observing that DO is truly ugly.... [asc]
I strongly disagree. DO is a construct that emphasizes the
notion that an iteration can proceed by initializing some state
variables and then repeatedly transforming them while maintaining
some invariant until a condition is reached. ... [gls]
I think Guy misguessed the source of my displeasure with DO. So I'll
clarify. (Warning: not a short message.)
I have no prima facie objection to the use of iterative constructs,
and in particular, none to supporting iteration in Scheme. Indeed, I think
that it is often very effective to think procedurally and iteratively rather
than functionally and recursively. (I understand these are apples and
oranges, but the styles are usually associated with each other.)
There may be interesting extremist arguments in favor of relying solely on
recursion for repetition, presumably based on strict minimalism and some
arguments concerning the elegance of recursion. But I probably wouldn't buy
them, and in any case that's not what my complaint is about. If we were going
to be minimalism extremists, we wouldn't provide IF, COND, and CASE in the same
language. Instead, I think we are trying to design an effective programming
environment while remaining "reasonably" elegant. The touchstone for the
appropriate degree of minimalism is that we provide the constructs that
a programmer will need, separating functionality out when the programmer's
abstraction of the control process is different (as opposed to merely the
underlying computation being different; hence CASE, IF, and COND).
So given the assumption that we are going to have one or more iteration
constructs, what should they look like and how should we select them?
My claim is that the DO we are using is a poor choice, and moreover,
that it probably reflects a correspondingly poor choice in selection criteria.
In a nutshell, DO does too much. It creates variables, binds them,
provides iteration, rebinds variables at tactically pleasing times,
tests a conditional expression, applies an implicit SEQUENCE to most
of its arguments, returns the result of evaluating an optionally present
expression... whew!
I submit that we have CommonLisp's DO (which is in use in other LISPS too,
of course) principally because it was being used by other LISPs and no one
really stopped to think what a good iteration construct for Scheme would
look like starting from first principles. We just grabbed what (some) (LISP)
programmers currently are using without treating this as an important
design problem.
I also submit that DO is too complex and that this complexity violates
two fundamental principles of good programming language construct design:
1. Keep constructs simple so people can learn, understand, read, debug,
and maintain them easily.
2. Each function should do one thing, and do it well. (No pun intended.)
Just to take a few pot shots at DO: we don't need variable binding and
creation, since we already have the LET family to do that nicely for us.
We don't need to confuse conditional exit from an iteration (i.e. using
a predicate expression) with FOR-class iteration that occurs, e.g.,
a predictable number of times and/or over a predictable set of values.
Certainly it's nice to have all these things around when you want them;
my point is simply that an iteration construct doesn't need to provide
all of them, that we can make intelligent choices about which ones
a given construct is to provide, and that if DO needs to contain all of
them, then the burden of proof is on those who would make that claim.
To reframe the challenge, the question is not whether you can come up
with times when you need conditional exit, and times when you need
FOR-style iteration, and... etc.; but rather, whether you can convincingly
demonstrate that all are needed in one iteration construct that appears in
the language definition.
Let me pose a few alternatives. Bear in mind that these are strawman
options, for illustrative purposes. If you don't like keywords in your
control constructs, imagine the examples without them.
(FOR i IN <list> DO <forms>) -- Evaluates <forms>, to which an implicit
SEQUENCE is applied, with i bound to successive values of <list>.
[This is like FOR-EACH except that you have the current value bound to
a lexically apparent locally-created locally-bound variable i. This is about
as similar to FOR-EACH as, say, COND and CASE are to each other.]
(VARYING i FROM n TO m BY s DO <forms>) -- Binds i to n, n+s, n+2s, ...
and evaluates <forms>, to which an implicit SEQUENCE is applied, for
each such binding, until i>m. Returns the result of the last evaluation
of <forms>.
[This is the classic FOR-loop construct used when you know the range
of values in advance, e.g. when you are stepping through a vector.]
(REPEAT n TIMES <forms>) -- Evaluates <forms>, to which an implicit
SEQUENCE is applied, n times. Returns the result of the last evaluation
of <forms>.
[Not frequently used, but highly perspicuous on those occasions when
this is exactly what you want to do.]
(WHILE <test> DO <forms>) -- Repeatedly evaluates <forms>, to which an
implicit SEQUENCE is applied, until <test> evaluates to #F, like
Pascal's WHILE.
[There's some interesting research by Jeff Bonar, among others,
with empirical results suggesting that Pascal's WHILE loop is actually
a dangerous, hard-to-learn construct. This is because (a) the classic
phase problem that occurs when you use a WHILE loop in a PROCESS,READ
paradigm is harder to learn than the more intuitive READ,PROCESS model,
and (b) beginners often think that WHILE really means "while," i.e.
"whenever <test> is true, do <forms>" or "the moment <test> would become
false, exit the loop." I also dislike the cooption of this word for this
iterative processing application, since its more intuitive meanings
actually might be useful in concurrent processing applications. In any
case, when not used in a PROCESS,READ paradigm, the construct (whatever
its name) is often quite useful.]
Hmm, that's a lot of extra stuff in a language to take the place of
one DO construct, isn't it? But that's precisely the point. DO is
a microcosm of MacLisp's and, by inheritance, Common Lisp's invasive
featurism. In the extreme, we could create a function F(x) and specify
which entire program we wanted simply by feeding F the proper number.
Many people would regard such a Goedlization of programs as a positive
step, if only they could determine which number to feed F. But: we wouldn't
call it programming; we wouldn't call F a "control construct" in the
sense that we normally use the word; and perhaps most importantly, we
wouldn't know how to meaningfully specify the x. Forgiving the hyperbole,
that is also true of DO: it is an expert's construct with options sticking
out all over and no coherent design principles underneath, hard to learn
and remember and even harder to read and understand quickly on sight.
I have performed the following informal experiment. I had one or
two of the people working with me who were true devotees of LOOP
and DO go back and recode fairly large (5000-15000 lines) LISP programs,
ripping out LOOP and DO and putting in DOLIST, DOTIMES, and mapping
functions. I should say that they did it "kicking and screaming," not
because of the work involved but because they so loved all the features
that LOOP offered. But a couple weeks later, they came back and said:
"You know, LOOP is really evil!"
"My code is infinitely easier to read and maintain now."
"I had no idea how ugly and impenetrable all that DO and LOOP code was
from all those `features' of DO and LOOP I was using."
"You have to have something seriously wrong with your head to be able to
use DO fluently."
"I'm not going to use LOOP again!"
I should say that the principal guy I have in mind here got his degree at
MIT. We're talking the hardest of sells, and when the dust had cleared,
he came to the conclusion that DO and LOOP are morally reprehensible.
We need to remember that programs are written not only to be executed,
but also to be read; and that well over 50% of programmer time is
spent maintaining existing code. Clear, clean, well-designed control
constructs can go a long way towards easing this burden. DO does not
seem to qualify as such a construct; rather, it seems like the incidental
union of numerous such constructs. We might be able to make a major
contribution to the utility of LISP in "practical" programming applications
by updating Scheme's iteration constructs so they provide better, cleaner,
more direct support for the variety of iteration models that are already
implicit in the code we write.
asc
∂14-Jul-86 0252 @MC.LCS.MIT.EDU:adams%tekchips.tek.csnet@CSNET-RELAY.ARPA Flaws of form
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From: Norman Adams <adams%tekchips.tek.csnet@CSNET-RELAY.ARPA>
Message-Id: <8607131704.AA21626@tekchips.TEK>
Subject: Flaws of form
To: rrrs-authors@MC.LCS.MIT.EDU
I would prefer to see no dedication in preference to making the dedication
serious. I think a serious dedication would read as insincere because
the Scheme report is an obvious parody of the Algol 60 report.
As much for my asusement as for anything else, I wrote this explanation:
The Algol 60 report is gravely earnest. Among its many firsts, Algol was
first to use a grammar-like construct to define its syntax. The first
report -- "Preliminary report - International Algebraic Language" -- as
well as the revision, were published as cover stories in the
@i(Communucations of the ACM) (*). The report was the culmination of an
international effort, followed with international attention. In the style
of world war commentary, the reader learns of the Zurich meeting, the Paris
meeting, and of the seven European representatives who held a final
prepatory meeting in Mainz in December 1959. And let us not forget the
seven American representatives with a similar quest, in Boston that same
year. We are spared the details of the lunch meats; judged, with Ph.D.
precision I am certain, to be expendable from the accounting. In each
re-reading, I look (in vain) for the mention of Teller and Oppenheimer;
surely they were involved too. It is in this intensely sober context that
we read the full page eulogy of William Turanski (**), who died after being
struck by a car the day before the 1960 conference in Paris.
(*) CACM v1 #12, 1958; CACM v6 #1, 1963
(**) CACM v3 #5, 1960, p 298
Scheme is fun and happy, and a bit quirky -- or are CDR and CAR and so many
relatives the ideal names for those procedures? Scheme is as serious as
LAMBDA, but as casual as CAR. Alas, what has become of dear PROGN? The
names are arbitrary and incidental; CAR and CDR remind us. Scheme is as
much an approach as a detailed concrete specification. But to be taken
seriously, for Scheme to be widely used, we must have the details and
concretions; they are essential but unimportant.
The Algol 60 report is almost ludicrous in its sobriety. If we use the form
of Algol 60 to present happy little Scheme, we cannot avoid the parody;
try as we might.
Still, I think there is good reason to use the form. Presenting Scheme in
the form of the Algol 60 report may capture the attention of those who
clump together and ignore all Lisp-like languages because the culture is so
different from what they know. The contrast with @i(Chine Nual) and
@i(CLtL) is important. Perhaps Lisp can be other than a bag of features of
a metastasizing runtime environment. Perhaps it can even be described in
the style of the day!
Following the model of Algol 60 exactly points out that the form of
description is itself an arbitrary convention; and the point is made in
perfect Scheme style. Just as Scheme can provide the "their" control
constructs, it can be described in "their" form.
The parody pokes fun at all those essential but unimportant details.
It is the perfect couch for Scheme.
So for all this, I find a serious dedication inappropriate. Algol 60's
dedication was grave; to an Algol soldier, killed in his prime (he was 35).
Scheme's dedication should be to something unimportant. "Dedicated to the
memory of dynamic binding.", as Jonathan once suggested, fits well. It
seems to me so much better than to try to be as somber and important as
Algol 60. I think we would look foolish in the attempt.
-Norman
-------
∂14-Jul-86 0325 @MC.LCS.MIT.EDU:adams%tekchips.tek.csnet@CSNET-RELAY.ARPA Flaws of form
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Date: Sun, 13 Jul 86 10:04:09 PDT
From: Norman Adams <adams%tekchips.tek.csnet@CSNET-RELAY.ARPA>
Message-Id: <8607131704.AA21626@tekchips.TEK>
Subject: Flaws of form
To: rrrs-authors@MC.LCS.MIT.EDU
I would prefer to see no dedication in preference to making the dedication
serious. I think a serious dedication would read as insincere because
the Scheme report is an obvious parody of the Algol 60 report.
As much for my asusement as for anything else, I wrote this explanation:
The Algol 60 report is gravely earnest. Among its many firsts, Algol was
first to use a grammar-like construct to define its syntax. The first
report -- "Preliminary report - International Algebraic Language" -- as
well as the revision, were published as cover stories in the
@i(Communucations of the ACM) (*). The report was the culmination of an
international effort, followed with international attention. In the style
of world war commentary, the reader learns of the Zurich meeting, the Paris
meeting, and of the seven European representatives who held a final
prepatory meeting in Mainz in December 1959. And let us not forget the
seven American representatives with a similar quest, in Boston that same
year. We are spared the details of the lunch meats; judged, with Ph.D.
precision I am certain, to be expendable from the accounting. In each
re-reading, I look (in vain) for the mention of Teller and Oppenheimer;
surely they were involved too. It is in this intensely sober context that
we read the full page eulogy of William Turanski (**), who died after being
struck by a car the day before the 1960 conference in Paris.
(*) CACM v1 #12, 1958; CACM v6 #1, 1963
(**) CACM v3 #5, 1960, p 298
Scheme is fun and happy, and a bit quirky -- or are CDR and CAR and so many
relatives the ideal names for those procedures? Scheme is as serious as
LAMBDA, but as casual as CAR. Alas, what has become of dear PROGN? The
names are arbitrary and incidental; CAR and CDR remind us. Scheme is as
much an approach as a detailed concrete specification. But to be taken
seriously, for Scheme to be widely used, we must have the details and
concretions; they are essential but unimportant.
The Algol 60 report is almost ludicrous in its sobriety. If we use the form
of Algol 60 to present happy little Scheme, we cannot avoid the parody;
try as we might.
Still, I think there is good reason to use the form. Presenting Scheme in
the form of the Algol 60 report may capture the attention of those who
clump together and ignore all Lisp-like languages because the culture is so
different from what they know. The contrast with @i(Chine Nual) and
@i(CLtL) is important. Perhaps Lisp can be other than a bag of features of
a metastasizing runtime environment. Perhaps it can even be described in
the style of the day!
Following the model of Algol 60 exactly points out that the form of
description is itself an arbitrary convention; and the point is made in
perfect Scheme style. Just as Scheme can provide the "their" control
constructs, it can be described in "their" form.
The parody pokes fun at all those essential but unimportant details.
It is the perfect couch for Scheme.
So for all this, I find a serious dedication inappropriate. Algol 60's
dedication was grave; to an Algol soldier, killed in his prime (he was 35).
Scheme's dedication should be to something unimportant. "Dedicated to the
memory of dynamic binding.", as Jonathan once suggested, fits well. It
seems to me so much better than to try to be as somber and important as
Algol 60. I think we would look foolish in the attempt.
-Norman
-------
∂14-Jul-86 0641 @MC.LCS.MIT.EDU:OXLEY%ti-csl.csnet@CSNET-RELAY.ARPA Re: Compatibility with Common Lisp: A meta comment
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Date: Mon 14 Jul 86 08:11:52-CDT
From: Don Oxley <OXLEY%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: Re: Compatibility with Common Lisp: A meta comment
To: RPG%su-ai@CSNET-RELAY.ARPA, rrrs-authors%mc.lcs.mit.edu@CSNET-RELAY.ARPA
In-Reply-To: Message from "Dick Gabriel <RPG@su-ai.ARPA>" of Sat 12 Jul 86 18:35:00-CDT
Message-Id: <12222608155.17.OXLEY@CSC60>
I must second Dick Gabriel's reply. A little "friendly rivalry" with
Common Lisp is fine, but the ultimate acceptance of Lisp (of either
dialect) is the crucial concern. I am probably as biased toward Scheme
as anyuone, but if Scheme is to succeed, it will owe a significant debt
to Common Lisp.
--Don
-------
∂14-Jul-86 0741 @MC.LCS.MIT.EDU:ramsdell%linus@mitre-bedford.ARPA Common Lisp
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Organization: The MITRE Corp., Bedford, MA
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Posted-Date: Mon, 14 Jul 86 10:38:32 edt
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Date: Mon, 14 Jul 86 10:38:32 edt
From: ramsdell%linus@mitre-bedford.ARPA
Message-Id: <8607141438.AA07736@jymme.sun.uucp>
To: rrrs-authors%mc.lcs.mit.edu@mitre-bedford.ARPA
Subject: Common Lisp
I certainly qualify an no fan of Common Lisp, however, I too would
like to point out a simple argument against gratuitous
incompatibilities with Common Lisp. Scheme's impact will be limited
if it is very difficult to convert CL code to Scheme, even if many
agree it is a superior language. The best way to port CL to Scheme is
in an environment that supports both languages. To me, Scheme would
be an excellent language in which to implement Common Lisp. A Scheme
implementation of Common Lisp would facilitate the conversion of CL
code by allowing versions the program to be written in a mixture of
both languages. Let's not make a Scheme implementation of Common Lisp
such a pain that no one will do it.
John
∂14-Jul-86 1008 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU [ANDY: dedication]
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Date: Mon, 14 Jul 86 13:08:53 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: [ANDY: dedication]
To: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].69636.860714.JAR>
Date: Mon 14 Jul 86 02:09:08-PDT
From: Andy Freeman <ANDY at sushi.STANFORD.EDU>
To: jar at AI.AI.MIT.EDU
Re: dedication
Message-ID: <12222563967.24.ANDY@sushi.STANFORD.EDU>
Has everyone else forgotten that Knuth dedicated his series to a 650
at case?
-andy
∂14-Jul-86 1337 @MC.LCS.MIT.EDU:RPG@SU-AI.ARPA Use of DO in Common Lisp Code
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Date: 14 Jul 86 1332 PDT
From: Dick Gabriel <RPG@SU-AI.ARPA>
Subject: Use of DO in Common Lisp Code
To: rrrs-authors@MC.LCS.MIT.EDU
I looked at a spectrum of code in the Lucid implementation of Common
Lisp to see how DO is used where DOLIST and DOTIMES could not
be used. The breakdown of use of iteration is this:
the frequency of use of DO is the same as the use of DOTIMES
and DOLIST combined
the use of LABELS/FLET is used as often as DOLIST.
The uses of DO in place of DOTIMES and DOLIST are interesting.
Sometimes the stepper is not CDR, so the use of DO is exactly
like DOLIST, but with the stepper (and end test) different; typically:
(DO ((current data-structure (next-data current)))
((empty-data current)) ...)
Sometimes the use is exactly like DOLIST, but the test is different.
(DO ((l l (cdr l)))
((end-test l))
(let ((x (car l)))
...))
But the most frequent use (by a margin of 3 to 1) is a combination of
DOTIMES and DOLIST:
(do ((l l (cdr l))
(i 0 (1+ i)))
((null l))
(let ((x (car l)))
...))
The use of DO outside of these paradigms is almost non-existent. Hairier
control structures are usually done with LABELS/FLET, and there are
3 large ATN's in the implementation, written with (glarg) TAGBODY.
One principle of Lisp design that DO follows is that the binding of the
iterator, its initial value, and its updator are apparent immediately upon
inspection - they are usually on one line. This principle is the basis of
(LET ((x value)) ...) being preferred to ((lambda (x ...) ...) value ...):
X and VALUE are not near each other on the page.
I don't have a proposal to make, but this data might be of use in thinking
about iteration in Scheme.
-rpg-
∂14-Jul-86 1448 @MC.LCS.MIT.EDU:goodhart%cod@nosc.ARPA Scheme Request
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Date: Mon, 14 Jul 86 14:25:46 PDT
From: Curtis L. Goodhart <goodhart%cod@nosc.ARPA>
Message-Id: <8607142125.AA13068@cod.ARPA>
To: scheme@mit-mc.ARPA
Cc: goodhart@nosc.ARPA
Subject: Scheme Request
-------
I am interested in obtaining a version of Scheme that will run on a
VAX 11/780 running VMS 4.2 OR a PDP-11/70 running Unix 2.9 .
Can you provide me some info on this?
I also recall that I may be able to FTP a copy of Scheme?
Are there user manuals available too?
Also, I will be at MIT in the Fall and probably take Ableson, and Sussman's
course, in which Scheme is used. Are there any crucial differences
between the version I might get through you and the version and MIT?
Thanks,
Curt Goodhart (goodhart@nosc on the arpanet)
-------
∂14-Jul-86 1514 @MC.LCS.MIT.EDU:andy@sun3.ads.ARPA Scheme vs. Common Lisp, #1: Politics
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Date: Mon, 14 Jul 86 14:31:19 PDT
From: andy@sun3.ads.ARPA (Andy Cromarty)
To: rrrs-authors%mit-mc@ads.arpa
Subject: Scheme vs. Common Lisp, #1: Politics
Cc: andy@ads.arpa, gls%think@ads.arpa, rpg%su-ai@ads.arpa
Reply-To: andy@ads.arpa
This is the first of two notes on CommonLisp vs. Scheme. I have
written two notes in an attempt to separate political concerns
from design concerns, in part to keep them clear in my own mind and
in part in consideration of those of you who, like me, generally
have neither the time nor the temperment for long political debates
on the ARPANET. This note concerns the politics, or what I
think of (perhaps a little unkindly) as the "form rather than
the content" of the CL-Scheme issue. Those of you who stick it out
and read through this note (and the ones that are sure to follow)
should bear in mind that, as we've already seen, politics is
necessarily a somewhat more personal discipline than is the
technology most of us are really interested in, and for that reason
writing styles for the political notes can be expected to differ
from those composed with primarily technical purposes in mind.
asc
------------------------------------------------------------------------
Shortly after receiving Dick's flame, the following scenario popped
into my head. You are listening in on a phone conversation somewhere
in Arlington, Virginia.
Squires: Clint, I hear a rumor that Andy Cromarty is concerned
about CommonLisp's influence on the development of
Scheme.
Kelly: Scheme?
Squires: Yes, another kinky LISP dialect being designed by some
researchers. It only has a fraction of CommonLisp's
features and they can't quite seem to decide what
it should look like.
Kelly: Well, Steve, I guess I'll have to ask you to simply
rescind DARPA's support for CommonLisp, then, and
from now on we'll require all our AI projects to
use Structured COBOL.
I suppose I should be flattered at the suggestion that a few sentences
from me would reshape the course of LISP history, especially coming as
it does from Dick Gabriel. But somehow I give the research funding
community and the commercial tool market a little more credit for
indepedence of thought than this scenario (or Dick's note) suggests.
Perhaps more importantly, I am somewhat troubled by the idea that
Dick would advocate censorship of ideas and opinions concerning LISP
design and development (viz. his instructions that we "Don't let
anyone outside this list see Andy's message."). My assumption is
that the RRRS-AUTHORS list exists for the purpose of supporting "open
discussion within a closed community" concerning what form Scheme
should take, and that we all implicitly agree to attempt to ground
our argumentation for our favored alternative views on a substantive
technical basis. In this regard, I probably agree with the
suggestion that my comment "represents a low point in political
thinking." I think the implied converse option -- that we all need
to suppress concern or public discussion about the *costs* of CL
compatibility, or for that matter, any other dangerous thoughts we
might have -- represents a new high water mark in politicization
of the Scheme design process, and I would not feel complimented to be
accused of having set that new standard. Certainly there are others
in the Scheme community with whom I disagree, but I cannot imagine
proposing (for example) that we censor Dan Friedman because his
ideas about internal DEFINE differ from mine. Quite the contrary: I
look forward to hearing why alternative views are held; and when I
decide I can't stand the heat, *I* get out of the kitchen.
But yes, please don't repeat my messages outside this community. I
think we all assume that our discussions are held reasonably private
by this community, since this is still a design-in-progress, and at
the present I'm sensitized by having been poorly quoted a little too
often in the press recently. (And anyway, if anyone at DARPA
wants to know what I think of CL, they have my phone number.)
Now let's take a good hard political look at who disagreed most
vocally with my comment. The few responses I've received so far all
have been from competent LISP designers and implementors, to be sure.
But it is also true that they have been from: the implementor(s) of
Texas Instruments' Common Lisp and Scheme products; the author of the
premier Common Lisp text; and the president of the most successful
and best know Common Lisp product company in the world. In addition,
many or most of these people were personally involved in the Common
Lisp design effort. Their credentials are impeccable, but their
goals and commitments may not be the same as those of, say, a
professor who is using Scheme for its pedagogical value and has no
career or financial stake per se in the long-term viability or
political acceptance of this year's best production quality LISP
environment. I certainly believe that having their views represented
is critical to a good Scheme's development, and I made it clear in my
original note that I do consider myself to be an outlying point in
the distribution of views on CL vs. Scheme. But I think they are,
too; and let us not assume that the most vociferous advocates of
extreme positions (myself included) represent either the norm or the
best compromise position to take.
Since Dick couldn't see from his location down the street that my
tongue was towards the side of my mouth when I used the term "dark
forces," let me say that (a) I think Common Lisp is one of the most
successful technology results of any standardization committee I've
seen and (b) my reference was to the risk of Scheme becoming just
like Common Lisp, rather than a criticism of the quality of Common Lisp
as a LISP. Overall, Common Lisp is very good at being what it tries to
be. I am utterly unconvinced that that's what Scheme is trying to
be, however. I will treat the question of the goals of the two
languages in my companion note, but for now suffice it to say that
the idea that these languages have (forgive the pun) common goals
strikes me as nonsensical. If that were true, we could submit Guy's
excellent book to SIGPLAN and retire this list. I might go so far as
to say that it is precisely because Scheme exists that Common Lisp
can be successful, in the following sense: Those of us who are
concerned with what LISP should look like for the next several
decades can preoccupy ourselves with design debates over Scheme
morality, while people like Dick and Guy go on to take a snapshot of
what the community knows about good LISP design and then integrate
that knowledge, addressing and overcoming all the political obstacles
along the way, to produce a viable, saleable LISP product. And good
luck to them; but I do not see that Lucid's chimeras need to be ours.
Rather than worry that people will learn that there is more than one
LISP, let's advertise the fact. Let's make it clear that LISP is an
ideal language for embedding new constructs in, and that the presence
of a good heavily-featured standardized dialect has not quenched the
long-standing historical drive for LISPers to remain at the
forefront of programming language and programming environment design.
Let's advocate a plethora of LISP-like languages to get people out of
the Pascal-derivative language design syndrome and instead get them
directly and cleanly addressing individual hard language design
problems, like the keyword shadowing problem, design of appropriate
multiprocessing constructs, embedding of evidential reasoning
techniques into a programming language, integration of advanced
database technology into the programming environment in a coherent
fashion, getting distributed inheritance graphs to work across
loosely-coupled processors, and (somebody, please!) developing a
reasonable model of I/O. Let's get them thinking that LISP is not
dead, that it is not a "solved problem," that it's there to
experiment with, and that there are and will continue to be good
reasons for all the debates we engage in on how languages should be
designed.
asc
p.s. Dick, if you're still pissed off at me, we can go out for
dinner at the LISP conference and you can throw darts at me.
∂14-Jul-86 1607 @MC.LCS.MIT.EDU:RPG@SU-AI.ARPA Politics
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Date: 14 Jul 86 1557 PDT
From: Dick Gabriel <RPG@SU-AI.ARPA>
Subject: Politics
To: rrrs-authors@MC.LCS.MIT.EDU
Naturally I'm not pissed at Andy. Were I truly pissed, and truly
flaming, my message would have begun, ``Andy, you total and complete
bagbiter, you are such a big loser that they had to extend the
city limits to include....''
My point was that I could imagine someone forwarding Andy's vitriol
to Common-Lisp or ARPA-BBOARDS and thereby lose some allies that
we, who are Scheme lovers one and all, would prefer to not lose if
at all possible.
Someday I'd like Lucid to be the ``most successful and best-known
supplier of Scheme products,'' on that happy day when Common Scheme
becomes the standard.
Homage, an item of low cost to the RRRS-authors, buys a lot from the
Common Lisp troops. Messages like Andy's, keyboard-in-cheek as they
may be, possibly buy more grief than the fun of typing them gains.
Politics and science are not so radically removed from each other. When
one propose some technical viewpoint, his goal is to have it accepted,
usually before he dies. Having his viewpoint accepted helps his
self-esteem, his quest for fame as a scientist, his reach for tenure. This
isn't much different from politics, in which the goals are probably
self-esteem, fame, and a reach for office. Although there may be more
technical content to a technical debate, the tactics used in arguing for a
political end really don't differ significantly.
This design committee should aim at producing the best possible Lisp.
If that happens to mean that nothing in it is like the corresponding
thing in Common Lisp, that's fine. All technical debate regarding these
choices should be open. If nothing in Scheme is like the corresponding thing
in Common Lisp simply because Common Lisp is bad, and disjointness is a
goal, then I think this design committee will have blown it.
********************************
On a related note, now that there has been a fair bit of experience with
Common Lisp, it might be worthwhile for this group to ask some of the
Common Lisp hackers about their experience with the parts of Common Lisp
that the Schemers find objectionable. Similarly, it might be instructive to
look at what the Common Lisp hackers find nice about Common Lisp that might
be surprising.
-rpg-
∂14-Jul-86 1702 @MC.LCS.MIT.EDU:dyb%iuvax.indiana.edu@CSNET-RELAY.ARPA call-with-xput-port vs. call-with-xput-file
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Date: Mon, 14 Jul 86 11:47:21 est
From: Kent Dybvig <dyb%iuvax.indiana.edu@CSNET-RELAY.ARPA>
To: rrrs-authors%mit-mc.CSNET@CSNET-RELAY.ARPA
Subject: call-with-xput-port vs. call-with-xput-file
I favor changing call-with-input-file and call-with-output-file to
call-with-input-port and call-with-output-port. However, I have some
questions related to the change and to ports in general.
1. I saw lots of confusion over the fact that you open a file (with
open-input-file and open-output-file) but close a port (with close-
input-port and close-output-port). Changing the "call-with" names
could increase the confusion. Should we change open-input-file and
open-output-file to open-input-port and open-output-port?
2. I have added string ports to Chez Scheme and need to choose names.
If we have call-with-...-file and open-...-file, I can introduce the
names call-with-...-string and open-...-string. On the other hand,
if we have call-with-...-port and open-...-port, I can introduce the
names call-with-...-string-port and open-...-string-port. The names
are longer but perhaps more descriptive. How do these names sound?
The point of this question is that any names we choose should
generalize to other types of ports.
3. Currently, there is no way to change the current ports to anything
other than a freshly-opened file (as with the inessential with-input-
from-file and with-output-to-file). Stylistically, I think it is
better to never change the standard ports. But if they can be changed,
I'd like to have a way for a debugger, say, to change them back to an
existing file (usually the original current ports), so that anything
the user executes goes to the expected place. Without this we cannot
hope to write a reliable portable debugger (and debug code with calls
to with-input-from-file or with-output-to-file).
4. Also, there is no way to change the current ports permanantly.
That is, it is not possible to write (set-current-input! <port>) or
(set-current-output! <port>). Again, I don't think this is good
practice, but some might rue the inability to do so.
5. Why is call-with-input-file essential and open-input-file not?
If call-with-input-file is analogous to call-with-current-continuation,
why do we not have (call-with-new-string <length> <proc>) instead of
make-string or (call-with-pair <obj1> <obj2> <proc>) instead of cons,
etc? Because call-with-current-continuation is special---a function
make-continuation would be problematic. In short, while I see the
merit in with-input-from-file since it closes the file and rebinds a
standard port, I cannot see the merit in call-with-input-file. Can
we flush call-with-input-file and call-with-output-file and promote
open-input-file and open-output-file to essential status?
∂14-Jul-86 1814 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Scheme Request
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Date: Mon, 14 Jul 86 20:58:54 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: Scheme Request
To: goodhart@NOSC-COD.ARPA
cc: goodhart@NOSC.ARPA, scheme@MC.LCS.MIT.EDU
In-reply-to: Msg of Mon 14 Jul 86 14:25:46 PDT from Curtis L. Goodhart <goodhart%cod at nosc.ARPA>
Message-ID: <[AI.AI.MIT.EDU].69927.860714.JAR>
Date: Mon, 14 Jul 86 14:25:46 PDT
From: Curtis L. Goodhart <goodhart%cod at nosc.ARPA>
I am interested in obtaining a version of Scheme that will run on a
VAX 11/780 running VMS 4.2 OR a PDP-11/70 running Unix 2.9 .
I think most or all of your questions are answered by the contents of
the file "LSPMAI;SCHEME IMPLS" available on Internet hosts MIT-MC,
MIT-MX, and MIT-AI (I have copied it around to improve its
accessibility, in case one or two of these machines are down).
By the way, I'll mail this file (about 17K) to anyone who requests it,
although if you can FTP it that's preferable. These machines aren't
finicky about usernames or passwords or things like that.
Jonathan
∂14-Jul-86 2156 @MC.LCS.MIT.EDU:dyb%iuvax.indiana.edu@CSNET-RELAY.ARPA the colon (:) in identifier syntax
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Date: Mon, 14 Jul 86 21:34:01 est
From: Kent Dybvig <dyb%iuvax.indiana.edu@CSNET-RELAY.ARPA>
To: rrrs-authors%mit-mc.CSNET@CSNET-RELAY.ARPA
Subject: the colon (:) in identifier syntax
Can we omit colon (:) from the enumeration of characters that can
be used in identifiers, to allow implementations to support some
sort of package system using colon as the separator?
∂14-Jul-86 2159 @MC.LCS.MIT.EDU:dyb%iuvax.indiana.edu@CSNET-RELAY.ARPA exp versus expt
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From: Kent Dybvig <dyb%iuvax.indiana.edu@CSNET-RELAY.ARPA>
To: rrrs-authors%mit-mc.CSNET@CSNET-RELAY.ARPA
Subject: exp versus expt
We have a way to find an exponent of e (exp n) and of an arbitrary
base (expt b n). We have a function to find the log base e (log n)
but not the log in an arbitrary base. How about adding (log n b)?
Why do we have (expt b n)? We could instead give exp an optional
argument specifying the base, i.e., (expt b n) => (exp n b). Why
is it not done this way in Common Lisp, as it is for log? Perhaps
because the argument order would seem backwards?
Kent
∂15-Jul-86 0951 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU convergence
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Date: Tue, 15 Jul 86 12:51:27 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: convergence
To: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].70360.860715.JAR>
Apparently we could go on forever thinking of and arguing over ways to
improve the language. If you have changes you want considered for the
SIGPLAN version of the report, please send them right way (actually,
send them in several months ago). Otherwise PLEASE just sit on them for
a while, and when this report is out, then let's start discussing the
next version. For now, orient your messages towards achieving
stability. If you want perfection then nothing will ever get published.
And, as they say in the soaps, I need to get on with my life.
Thanks
Jonathan
∂15-Jul-86 1807 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: Scheme's DO construct
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To: rrrs-authors@MC.LCS.MIT.EDU
Subject: Re: Scheme's DO construct
Date: 15 Jul 86 15:52:52 PDT (Tue)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
There are two things to be said in defense of Scheme's DO:
1. Unlike most general purpose iteration constructs, DO is useful
for functional programming.
2. DO is the only general purpose iteration construct in Scheme
that doesn't force you to think up a name (such as LOOP) for
the loop.
This is a long message, but the two points above are the gist of it.
It seems to me that Andy has missed the first point entirely, considering
his remarks that:
I have no prima facie objection to the use of iterative constructs,
and in particular, none to supporting iteration in Scheme. Indeed, I
think that it is often very effective to think procedurally and
iteratively rather than functionally and recursively. (I understand
these are apples and oranges, but the styles are usually associated
with each other.)
...
I have performed the following informal experiment. I had one or
two of the people working with me who were true devotees of LOOP
and DO go back and recode fairly large (5000-15000 lines) LISP programs,
ripping out LOOP and DO and putting in DOLIST, DOTIMES, and mapping
functions. I should say that they did it "kicking and screaming," not
because of the work involved but because they so loved all the features
that LOOP offered.
LOOP is indefensible, but Andy is mistaken to lump DO with LOOP.
If by "mapping functions" Andy here means the standard Scheme mapping
functions, then MAP is the only functional alternative to DO that Andy
offered his people. MAP isn't general enough to replace DO, and DOLIST,
DOTIMES, and FOR-EACH are completely useless for functional programming.
Thus it seems that in the name of style Andy was coercing his people to
convert functional programs that use DO into non-functional programs.
It seems to me that if we truly want to discourage people from writing
functional programs, a more effective way to do it would be to change
Scheme so people can't program in the functional style until they master
a set of arbitrarily chosen rules for inserting tokens like #' and FUNCALL
into their programs.
Let's consider the functional alternatives to DO using a simple example.
The example is not too simple; it cannot easily be written using Scheme's
standard mapping procedures. (Aside: In the example, SEQUENCE is a
procedure, not a special form, so this is not portable Scheme code.
The name SEQUENCE was meaningful to my audience, so I used it anyway.
As I recall the discussion at Brandeis, SEQUENCE as a special form was
supposed to disappear over time so we could use the name for such higher
purposes, and I was very disappointed that the recent vote was phrased
as a referendum on dropping BEGIN rather than on dropping SEQUENCE.)
The example is:
(define find-word-break
(lambda (x k2)
(do ((x x (rest x)))
((or (empty? x) (not (break? (first x))))
(do ((x x (rest x))
(word '() (concat word (sequence (first x)))))
((or (empty? x) (break? (first x)))
(k2 word x)))))))
The most straightforward elimination of DO yields:
(define find-word-break
(lambda (x k2)
(letrec ((loop1
(lambda (x)
(if (or (empty? x) (not (break? (first x))))
(letrec ((loop2
(lambda (x word)
(if (or (empty? x) (break? (first x)))
(k2 word x)
(loop2 (rest x)
(concat word
(sequence (first x))))))))
(loop2 x '()))
(loop1 (rest x))))))
(loop1 x))))
This code is rather forbidding, so I would probably define loop1 and loop2
in a single LETREC. That works in this case but would not work if a
variable introduced by the outer DO were free within the inner DO.
REC or NAMED-LAMBDA would improve the code a little.
Can Scheme do better? I could instead use named LET, which would have
the advantage of moving the initialization expression for each loop
variable into proximity with its binding, and would make some of the
LAMBDAs invisible:
(define find-word-break
(lambda (x k2)
(let loop1
((x x))
(if (or (empty? x) (not (break? (first x))))
(let loop2
((x x)
(word '()))
(if (or (empty? x) (break? (first x)))
(k2 word x)
(loop2 (rest x)
(concat word (sequence (first x))))))
(loop1 (rest x))))))
This version still has two disadvantages: (1) I had to think about (or avoid
thinking about!) the names LOOP1 and LOOP2; and (2) it is hard to find the
new bindings for the loop variables. The way to overcome these disadvantages
is to invent a new special form that moves the expressions that compute the
new values for the loop variables next to their bindings (Dick Gabriel has
already pointed out the value of doing this) and to suppress the names of
the loops; in other words, to invent DO.
Having invented DO, we still have to decide on its syntax. The syntax of
Scheme's DO is less than optimal for functional programming primarily
because it is designed to support an additional feature: you can insert
non-functional statements to be executed every time around the loop.
Because Scheme is not a purely functional language, this is a reasonable
feature to support; even I use it on occasion. Unless we can come up with
a significantly better syntax, we might as well enjoy the advantages of
Lisp tradition and compatibility, while fixing any randomness (as we did
by flushing the implicit binding of RETURN and by using binding instead of
assignment for the loop variables).
I could go on and talk about why functional loops such as the ones you
write using tail recursion or DO are easier to understand than imperative
loops such as the ones you write using DOTIMES, DOLIST, FOR-EACH, or
Andy's straw FOR, VARYING, REPEAT, or WHILE, but I don't think it's
necessary for this audience.
Peace, William Clinger
∂15-Jul-86 2019 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU rrrs-authors
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Date: Tue, 15 Jul 86 23:19:07 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: rrrs-authors
To: adams%tekchips.tek.csnet@CSNET-RELAY.ARPA
cc: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Tue 15 Jul 86 14:30:07 PDT from Norman Adams <adams%tekchips.tek.csnet at CSNET-RELAY.ARPA>
Message-ID: <[AI.AI.MIT.EDU].70741.860715.JAR>
Date: Tue, 15 Jul 86 14:30:07 PDT
From: Norman Adams <adams%tekchips.tek.csnet at CSNET-RELAY.ARPA>
To: jar at AI.AI.MIT.EDU
Re: rrrs-authors
Message-Id: <8607152130.AA18643@tekchips.TEK>
Who is on the rrrs-authors list? I'm just curious ... -N
Here's the current membership of the list. It's pretty much the same
people as were on the SCHEME mailing list before it was opened up to the
general public.
- Jonathan
;;; -*- Mode:LISP; -*-
;;; Authors of the Revised↑3 Report on the Algorithmic Language Scheme
;;; To be added or deleted, send mail to SCHEME-REQUEST.
;;; Sorted alphabetically by name of institution, and alphabetically
;;; within institution, except for MIT, which appears first.
(file [LSPMAI;RRRS MAIL]) ;Local archive file
(SCHEME-RRRS MIT-OZ) ;Oz people
;;; Also on SCHEME-TEAM
(LS.SRB EE)
(cherian vx)
YEKTA ;Yekta Gursel
JAR ;?
(katz vx)
(alco vx)
(CPH AI)
;;; Others
ALAN
NICK ;Nick Papadakis
RHH ;Bert Halstead
Daniel ;Daniel Weise
RDZ ;Ramin Zabih
;;; Non-MIT
(jleech aids-unix) ;AI & DS / Jay Leech
(william aids-unix) ; William Bricken
(andy aids-unix) ; Andy Cromarty
(wand%northeastern CSNET-Relay) ;Brandeis / Mitch Wand
(dyb%indiana CSNET-Relay) ;Indiana / Kent Dybvig
(scheme-rrrs%indiana CSNET-Relay) ;Indiana / ...
(linus!ramsdell Mitre-Bedford) ;MITRE / John Ramsdell
("#COMSCH.MSG[SCH,LSP]" SU-AI) ;Stanford / File archive
(ANDY SU-SUSHI) ; Andy Freeman
(RPG SU-AI) ; Dick Gabriel
KMP ;Symbolics / Kent Pitman
(adams%tekchips%tektronix csnet-relay) ;Tektronix / Norman Adams
(willc%tekchips%tektronix csnet-relay) ; Will Clinger
(Scheme-Local%TI-CSL CSNET-Relay) ;TI / ...
GLS ;TMI / Guy Steele
(patel CS.UCLA.EDU) ;UCLA / Dorab Patel
(Hudak Yale) ;Yale / Paul Hudak
(Kelsey Yale) ; Richard Kelsey
(Kranz Yale) ; David Kranz
(Philbin-Jim Yale) ; Jim Philbin
∂15-Jul-86 2105 @MC.LCS.MIT.EDU:jleech@sun6.ads the rrrs authors
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Date: Tue, 15 Jul 86 21:03:00 PDT
From: jleech@sun6.ads (Jay Leech)
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: the rrrs authors
Cc: andy@sun3.ads.ARPA
Myself and a couple of others on the rrrs-authors mailing list were
associated with AI & DS.
We have changed our company name to Advanced Decision Systems, and
our arpanet address should now be ads or ads-unix.
Also, good work! I am looking forward to the publication of the report.
-- Jay Leech
∂16-Jul-86 1731 @MC.LCS.MIT.EDU:brooks%tilde%TI-CSL.CSNET@CSNET-RELAY.ARPA Substring & friends
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Date: Wed, 16 Jul 86 11:01:18 cdt
From: Gary Brooks <brooks%tilde%TI-CSL.CSNET@CSNET-RELAY.ARPA>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: Substring & friends
As stated in the R↑3 Report, the documentation for the <start> and <end>
indices for substring & friends is consfused. The report states that
<start> and <end> must be valid indices (with <start> <= <end>). This
is certainly not the case if you are taking the substring of an entire
string, where the index for <end> must be one greater than the largest
valid index. The previous report, RRRS, included a paragraph explaining
that <start> is inclusive and <end> is exclusive, which is clearer
though still inconsistant with the documentation for substring. This
inconsistency should be rectified.
On the other hand <start> and <end> could be defined to both be
inclusive. Now, I realize that there are probably too many instances of
substring & friends running around, and that this would be incompatible
with CL's subsequence, but I for one dislike the notion of (exclusive)
indices that may not be (really) valid indices. Comments?
-- brooks
∂16-Jul-86 1732 @MC.LCS.MIT.EDU:Bartley%TI-CSL.CSNET@CSNET-RELAY.ARPA Re: number syntax
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Date: Wed 16 Jul 86 10:53:32-CDT
From: David Bartley <Bartley%TI-CSL.CSNET@CSNET-RELAY.ARPA>
Subject: Re: number syntax
To: JAR%ai.ai.mit.edu@CSNET-RELAY.ARPA
Cc: rrrs-authors%mc.lcs.mit.edu@CSNET-RELAY.ARPA,
Bartley%TI-CSL.CSNET@CSNET-RELAY.ARPA
In-Reply-To: <860710120911.5.JAR@ROCKY-GRAZIANO.LCS.MIT.EDU>
Message-Id: <12223161873.35.BARTLEY@CSC60>
> Date: Thu, 10 Jul 86 12:09 EDT
> From: Jonathan A Rees <JAR%ai.ai.mit.edu@CSNET-RELAY.ARPA>
>
> Date: Tue 17 Jun 86 16:00:31-CDT
> From: David Bartley <Bartley%ti-csl.csnet at CSNET-RELAY.ARPA>
>
> One irritant in the Report that we have neglected to comment on until
> now (sorry!) is the syntax of numbers. We believe that Scheme numbers
> are essentially equivalent to Common Lisp numbers except for the new
> notion of exactness. To the extent that that is so, it seems to be a
> (shudder!) ``gratuitous difference'' from Common Lisp to have an
> incompatible syntax. [...]
>
> What we'd like to see is an essential syntax for numbers which is
> compatible with Common Lisp's. Additional features, including
> exactness, would be optional extensions. Even so, they should not
> conflict with Common Lisp. For example, the use of `#s' and the order
> of <sign> and <prefix> are different in the two languages. [...]
>
> Does anyone agree with us? Is there time to make such a change before
> R↑3RS goes to press?
>
>I think everyone agrees with you, and that there is time. Could you
>please write a concrete proposal, preferably something close to being
>suitable for inclusion in the report. Also please provide BNF. Thanks.
>
>Jonathan
Here's a stab at it---we expect and welcome debate over the details.
The major differences between the syntax of numbers in Common Lisp (CL)
and heretofore in Scheme (R↑3RS) are:
(1) CL has the prefix denoting base precede the sign; R↑3RS has the sign
precede the prefix, which includes the base specifier. I see no reason to
differ from CL.
(2) CL uses several exponent markers to specify levels of precision for
floating point numbers; R↑3RS specifies precision levels (S and L) in the
prefix. Again, why differ from CL?
(3) CL does not provide for the use of `#' to indicate insignificant
digits. Making this a non-essential feature in R↑3RS seems reasonable.
(4) CL provides only the #C(real real) notation for complex numbers; R↑3RS
provides infix notations for both polar and rectangular forms. For
compatibility with CL, R↑3RS should support the #C notation and the infix
forms should be non-essential extensions.
(5) CL integers may optionally terminate in a decimal point; R↑3RS permits
such a number to be treated as floating point and it is debated whether it
is to be considered exact. This is a serious problem, since many
procedures are defined to accept only integer values. Is the call
(INTEGER->CHAR 55.) valid? We propose that this be a non-essential
feature in R↑3RS.
(6) CL integers and ratios are not permitted to have exponent markers.
This feature should be a non-essential extension to Scheme.
(7) CL does not have the concept of exactness. Most (all?) existing
implementations of Scheme do not support this feature, so it should be
non-essential.
We propose the following syntax for numbers in Scheme. (Recall that
letter case is insignificant in the grammar and that the rules for <ureal
R>, <prefix R>, etc., should be replicated for R = 2, 8, 10, and 16.)
<number> --> <real> | #c( <real> <real> )
<real> --> <prefix R> <sign> <ureal R>
<prefix R> --> <exactness> <radix R>
<exactness> --> <empty> | #i | #e
<radix 2> --> #b
<radix 8> --> #o
<radix 10> --> <empty> | #d
<radix 16> --> #x
<sign> --> <empty> | + | -
<ureal R> --> <integer R> | <ratio R> | <flonum R>
<integer R> --> <digit R>+ #*
<ratio R> --> <digit R>+ #* / <digit R>+ #*
<flonum R> --> . <digit R>+ #* <expon>
| <digit R>+ . <digit R>* #* <expon>
| <digit R>+ #* . #* <expon>
<expon> --> <empty> | <expon-marker> <sign> <digit>+
<expon-marker> --> e | f | d | l | s
<digit 2> --> 0 | 1
<digit 8> --> 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7
<digit 10> --> <digit 8> | 8 | 9
<digit 16> --> <digit 10> | a | b | c | d | e | f
Although we have incorporated <exactness> and the use of `#' above, they
should be stated to be non-essential features of Scheme.
Nonessential feature: integers with optional decimal points.
<integer R> --> <digit R>+ #* .
Nonessential feature: integers and ratios with exponents.
<integer R> --> <digit R>+ #* <expon>
<ratio R> --> <digit R>+ #* <expon> / <digit R>+ #* <expon>
Nonessential number productions representing complex numbers. We worry
that the forms <real>+<ureal>i and <real>-<ureal>i can be hard to parse.
Perhaps combining the suffix `i' with the infix `+' or `-' would be
palatable to those who want this feature.
<number> --> <real> +i <ureal>
| <real> -i <ureal>
| <real> @ <real>
Regards,
David Bartley
Mark Meyer
-------
∂16-Jul-86 1921 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU July 15 draft sent
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Date: Wed, 16 Jul 86 22:21:24 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: July 15 draft sent
To: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].71397.860716.JAR>
Today I US-mailed another draft to everyone (except GLS, KMP, and people
at MIT, who I'll get to Thursday or Friday, or who can steal them from
my desk). It is closer to done than the previous one was, but note that
it does NOT reflect any changes in number syntax, LOAD, or names of
call-with-*put-port. There are a few other things I didn't get to,
which I can't recall right now, but I'm confident that y'all will miss
them and tell me.
I probably won't start another pass over it until a week from tomorrow
(i.e. the 17th), so don't feel guilty if you don't send your remarks to
me before that. After the 20th is when you can start feeling guilty.
Jonathan
∂17-Jul-86 0851 @MC.LCS.MIT.EDU:CPH@AI.AI.MIT.EDU Substring & friends
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Date: Thu, 17 Jul 86 11:50:46 EDT
From: Chris Hanson <CPH@AI.AI.MIT.EDU>
Subject: Substring & friends
To: brooks%tilde%TI-CSL.CSNET@CSNET-RELAY.ARPA
cc: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Wed 16 Jul 86 11:01:18 cdt from Gary Brooks <brooks%tilde%TI-CSL.CSNET at CSNET-RELAY.ARPA>
Message-ID: <[AI.AI.MIT.EDU].71736.860717.CPH>
I object to changing the substring indexing scheme. I chose the
imbalanced inclusive-start/exclusive-end pair because it has a some
nice properties:
1. The pair for the entire string is (0, length(string)), which is
trivially computable.
2. The pair for the empty string is (i, i) for any i <=
length(string). There is no natural representation for this if both
indices are inclusive.
Don't think that no thought went into this. I know that on first
encountering this scheme it seems unintuitive, but experience has
shown it to be quite effective, and once learned, easy to remember.
I don't think that the issue of whether or not the end index is a
valid index for the string is very interesting. In practice, it is
easy to decide whether a given index pair is valid:
0 <= start <= end <= length(string)
∂17-Jul-86 1217 @MC.LCS.MIT.EDU:GJS%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU Re: Substring & friends
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Date: Thu 17 Jul 86 13:09:44-EDT
From: "Gerald Jay Sussman" <GJS%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>
Subject: Re: Substring & friends
To: CPH@AI.AI.MIT.EDU, rrrs-authors@MC.LCS.MIT.EDU
In-Reply-To: <[AI.AI.MIT.EDU].71736.860717.CPH>
Message-ID: <12223437888.36.GJS@OZ.AI.MIT.EDU>
I agree with CPH about his choice of "half-open interval"
representations of strings. I believe that the choice he made is
pretty optimal because of good nesting and adjacency relations that
are clear if one thinks abstractly.
-------
∂17-Jul-86 1412 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU [jtv%fingate.bitnet: Scheme Request]
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Date: Thu, 17 Jul 86 16:39:45 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: [jtv%fingate.bitnet: Scheme Request]
To: scheme@MC.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].71910.860717.JAR>
If someone could translate the following for me, or even identify what
language it's written in, I'd be grateful.
Thanks,
Jonathan
Date: Tue, 15 Jul 86 20:12:38 +0200
From: Jukka Virtanen <jtv%fingate.bitnet at WISCVM.ARPA>
To: JAR at AI.AI.MIT.EDU
Re: Scheme Request
Tjaah, ei meilla KAI ole schemea...
JOs on, en tieda siita. Juha Heinasella (tre)
jh@tut on sellainen REF manual, jota ketselin
katselin
chanlmersiin mentaessa.
Etkos tilannut scheme listat?
Vois ton tilata tuolta, jos viitsit.
Juki
∂17-Jul-86 1442 @MC.LCS.MIT.EDU:adams%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: Substring & friends
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Date: Thu, 17 Jul 86 09:44:56 PDT
From: Norman Adams <adams%tekchips.tek.csnet@CSNET-RELAY.ARPA>
Message-Id: <8607171644.AA10005@tekchips.TEK>
Subject: Re: Substring & friends
To: Gary Brooks <brooks%tilde%TI-CSL.CSNET@CSNET-RELAY.ARPA>
Cc: rrrs-authors@MC.LCS.MIT.EDU
In-Reply-To: Gary Brooks <brooks%tilde%TI-CSL.CSNET@csnet-relay.CSNET>, Wed, 16 Jul 86 11:01:18 cdt
On the other hand <start> and <end> could be defined to both be
inclusive. Now, I realize that there are probably too many instances of
substring & friends running around, and that this would be incompatible
with CL's subsequence, but I for one dislike the notion of (exclusive)
indices that may not be (really) valid indices. Comments?
Here's a comment:
Currently, if given <start> and <length>, then <end> = <start> + <length>;
whereas with inclusive indices <end> = <start> + <length> - 1. I prefer
to not have to adjust by 1 in index computations.
-Norman
-------
∂18-Jul-86 0012 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: Substring & friends
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To: brooks%tilde%TI-CSL.CSNET@CSNET-RELAY.ARPA
Cc: rrrs-authors@MC.LCS.MIT.EDU
Subject: Re: Substring & friends
In-Reply-To: Your message of Wed, 16 Jul 86 11:01:18 cdt.
<8607170501.AA05456@tekchips.TEK>
Date: 17 Jul 86 15:28:38 PDT (Thu)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
An advantage of an inclusive <start> and an exclusive <end> is that
(substring s 0 (string-length s)) is the entire string. If both
were inclusive you'd have to say (substring s 0 (-1+ (string-length s))),
which seems less convenient. Using (- x 1) instead of (-1+ x) makes it
even harder to read.
An aside on -1+: As Marianne Moore said, I too dislike it. I can't
agree that it can't be pronounced, however, since I pronounce (-1+ x)
as "the predecessor of x" or "one less than x". As Kent Pitman once
pointed out, we can pronounce things however we like. (Kent wanted
things like EQ? to be pronounced "eek-pee". I propose that EQ? be
pronounced "eek-hunh?", with a rising inflection. Just kidding.)
By the way, I don't care whether 1+ and -1+ go or stay; whatever
Jonathan decides is fine with me.
Peace, Will
∂18-Jul-86 1428 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU [jtv%fingate.bitnet: Scheme Request]
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Date: Fri, 18 Jul 86 17:22:04 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: [jtv%fingate.bitnet: Scheme Request]
To: scheme@MC.LCS.MIT.EDU
In-reply-to: Msg of Fri 18 Jul 86 12:01:19 MDT from Fons Botman <mcvax!vu44!fons at seismo.CSS.GOV>
Message-ID: <[AI.AI.MIT.EDU].72425.860718.JAR>
Thanks to everyone who replied to my query about the Finnish mail I
received.
Jonathan
∂21-Jul-86 0448 @MC.LCS.MIT.EDU:ramsdell%linus@mitre-bedford.ARPA typos
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Organization: The MITRE Corp., Bedford, MA
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Posted-Date: Mon, 21 Jul 86 07:35:50 edt
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Date: Mon, 21 Jul 86 07:35:50 edt
From: ramsdell%linus@mitre-bedford.ARPA
Message-Id: <8607211135.AA12384@jymme.sun.uucp>
To: rrrs-authors%mc.lcs.mit.edu@mitre-bedford.ARPA
Subject: typos
1) [Page 5, col 2, line 8] atsign => at-sign.
2) [Page 5, col 2, line -1] The note seems out of place.
I suggest deleting it.
3) [Page 5, col 1, line 19] #fand => #f and.
4) [Page 9, col 1, line 21] Odd indent.
5) [Page 10, col 2] Program example not indented correctly.
6) [Page 10, col 2, line -l] comma/at-sign/expression =>
comma at-sign expression OR comma-at-sign-expression.
7) [Page 12, col 2, line -14] In the phrase "equal? is the coarsest
or most liberal", liberal has too many meanings; I suggest
dropping the phrase "or most liberal".
8) [Page 20, col 1, line -20] rouding => rounding.
9) [Page 22, col 2, line -19] uppper => upper.
10) [Page 27, col 2] call-with-xxput-file => call-with-xxput-port.
11) [Page 38, col 1, ref 14] No page numbers.
Wow! What an improvement!
John
∂21-Jul-86 0737 @MC.LCS.MIT.EDU:Mike←Wilson%CARLETON.BITNET@WISCVM.WISC.EDU Performance and Evaluation of Scheme Systems...
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Date: 21 Jul 86 08:04:00 EDT
From: Mike Wilson <Mike←Wilson%CARLETON.BITNET@WISCVM.WISC.EDU>
To: scheme%mc.lcs.mit.edu@CSNET-RELAY.ARPA
MMDF-Warning: Parse error in original version of preceding line at CSNET-RELAY.ARPA
Subject: Performance and Evaluation of Scheme Systems...
Hi,
I've just been looking through the book ←Performance and Evaluation
of Lisp Systems← (Richard P. Gabriel, The MIT Press). It's got benchmark
results for several simple programs run on the more common lisp systems.
Has anyone run these tests in CScheme/MacScheme/TIScheme? It would be
interesting to see how we stack up. (I have to admit I am *impressed*
with their times for the IBM 3081 and CRAY-XMP. Oh well...)
.Mike
∂21-Jul-86 0808 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU schedule
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Date: Mon, 21 Jul 86 11:00:01 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: schedule
To: ramsdell%linus@MITRE-BEDFORD.ARPA
cc: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Mon 21 Jul 86 07:47:45 edt from ramsdell%linus at mitre-bedford.ARPA
Message-ID: <[AI.AI.MIT.EDU].73291.860721.JAR>
Date: Mon, 21 Jul 86 07:47:45 edt
From: ramsdell%linus at mitre-bedford.ARPA
I cannot keep up with your schedule. I received the July 15th draft
on Friday afternoon, and did not have access to a computer until this
morning. There is no way I could have gotten my reply to you by July
20th.
Jeez, did I tell people to send me comments by the 20th? I meant to say
that I won't be doing anything until the 24th, so don't kill yourself to
get stuff to me before that. Within 5 days after the 24th would be very
nice. The main guideline is this: the report must absolutely be in its
final form before the Lisp conference; in fact, it probably has to be
done by Thursday July 31, so that there's time to make zillions of
copies of it to hand out at the conference.
Jonathan
∂21-Jul-86 0827 @MC.LCS.MIT.EDU:CLOWNEY@BLUE.RUTGERS.EDU Logic Continuations (Abstract)
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Date: 21 Jul 86 11:11 EDT (Mon)
From: Les <Clowney@BLUE.RUTGERS.EDU>
To: Chris Haynes <cth%indiana.csnet@CSNET-RELAY.ARPA>
Cc: scheme@MC.LCS.MIT.EDU, clowney@BLUE.RUTGERS.EDU
Subject: Logic Continuations (Abstract)
Hi Chris,
I am generally interested in reports on Scheme that have come
out of Indiana University, and am currently interested in the report
on continuations as applied to the implementation of logic programming in
Scheme (Computer Science Department Technical Report No. 183). Where
should I inquire about this report and a general index of Scheme
related reports?
les
∂21-Jul-86 1014 @MC.LCS.MIT.EDU:gls@Think.COM Scheme's DO construct
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Date: Mon, 21 Jul 86 12:37 EDT
From: Guy Steele <gls@Think.COM>
Subject: Scheme's DO construct
To: andy@AIDS-UNIX.ARPA, rrrs-authors%mit-mc@AIDS-UNIX.ARPA
Cc: gls@AQUINAS.ARPA
In-Reply-To: <8607132227.AA23925@Zarathustra.Think.COM>
Message-Id: <860721123716.3.GLS@BOETHIUS.THINK.COM>
Well, you have constructed a great case based on anecdotal evidence,
which is worth having, but I think you have not even addressed my main
point. The other constructs you mentioned (FOR, REPEAT, and WHILE) have
what I regard as an important flaw: a reliance on side effects to
accomplish some part of the iterative process. There is seldom any use
in stepping just one variable in an iteration; you want to step two or
more. Because FOR, REPEAT, and WHILE (and for that matter DOLIST and
DOTIMES) each step at most one variable, it is necessary to have some
side effect in the body to get anything done.
DO is the only iteration construct we have (other than LOOP) that
encapsulates completely the notion of iteration: the iterative
transformation of a state (normally a compound state, therefore
consisting of two or more quantities) in such a way that an invariant is
maintained at each step, terminated when the state satisfies some
condition. The problem is not that DO has too many features, but that
each of the other iteration constructs is incomplete in a way that must
be patched up using side effects.
I would be quite happy to eliminate one feature of DO: the body! If the
body is used, then side effects are necessarily involved. The most
perspicuous uses of DO have no body.
The other problem with DO is that sometimes there is more than one
reason to exit. I admit that as a flaw; but then again, sometimes there
is reason to return more than one value from a function, and I believe
SCHEME is not yet addressing that either with explicit features.
(Having a body compensates somewhat for that:
(defun memq (x l)
(do ((z l (cdr z)))
((null z) nil)
(when (eql x (car z)) (return z))))
This leads me to propose that a good iteration construct would be
like DO but instead of having a body would have more COND clauses.)
--Guy
∂21-Jul-86 1057 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: Performance and Evaluation of Scheme Systems...
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Date: Mon 21 Jul 86 10:52:21-CDT
From: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: Re: Performance and Evaluation of Scheme Systems...
To: Mike←Wilson%CARLETON.BITNET%wiscvm.wisc.edu@CSNET-RELAY.ARPA,
scheme%mc.lcs.mit.edu@CSNET-RELAY.ARPA
Cc: Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
In-Reply-To: Message from "Mike Wilson <Mike←Wilson%CARLETON.BITNET%wiscvm.wisc.edu@CSNET-RELAY.ARPA>" of Mon 21 Jul 86 08:04:00-CDT
Message-Id: <12224472379.36.BARTLEY@CSC60>
>Date: 21 Jul 86 08:04:00 EDT
>From: Mike Wilson
>Subject: Performance and Evaluation of Scheme Systems...
>
> I've just been looking through the book ←Performance and Evaluation
>of Lisp Systems← (Richard P. Gabriel, The MIT Press). It's got benchmark
>results for several simple programs run on the more common lisp systems.
>Has anyone run these tests in CScheme/MacScheme/TIScheme? It would be
>interesting to see how we stack up. (I have to admit I am *impressed*
>with their times for the IBM 3081 and CRAY-XMP. Oh well...)
I will be presenting a paper on TI's PC Scheme at the conference on LISP
and Functional Programming in Cambridge the first week of August. Part of
the paper consists of a brief comparison of PC Scheme and other PC-based
LISP implementations on 7 benchmark programs, some of which come from
Gabriel's test suite. After the conference, I'll be glad to forward this
information to anyone interested.
Regards,
David Bartley
-------
∂21-Jul-86 1143 @MC.LCS.MIT.EDU:bc@MEDIA-LAB.MIT.EDU Bobcat scheme
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Date: Mon, 21 Jul 86 14:38:21 EDT
From: William H Coderre <bc@MEDIA-LAB.MIT.EDU>
Message-Id: <8607211838.AA03625@MEDIA-LAB.MIT.EDU>
To: scheme@mc.lcs.mit.edu
Subject: Bobcat scheme
I did a rather trivial test between CScheme on Bobcat and MacScheme.
I suspect my data, since it appeared that CScheme was GCing a LOT.
Silly Question:
Does anybody know offhand how to tell unix to give Scheme more memory?
We have the "deluxe" bobcats with graphics stuff andapproximately 8
megs of core, and we'd like to use them!
"Tzima Narki"............................................................bc
∂21-Jul-86 1228 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Logic Continuations (Abstract)
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Date: Mon, 21 Jul 86 15:06:42 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: Logic Continuations (Abstract)
To: Clowney@BLUE.RUTGERS.EDU
cc: cth%indiana.csnet@CSNET-RELAY.ARPA, scheme@MC.LCS.MIT.EDU
In-reply-to: Msg of 21 Jul 86 11:11 EDT (Mon) from Les <Clowney at BLUE.RUTGERS.EDU>
Message-ID: <[AI.AI.MIT.EDU].73379.860721.JAR>
Date: 21 Jul 86 11:11 EDT (Mon)
From: Les <Clowney at BLUE.RUTGERS.EDU>
... Where should I inquire about this report and a general index of
Scheme related reports?
I'm trying to maintain a moderately thorough bibliography. Here's what
it looks like at present (this is the bibliography for the new version
of the scheme report). If anyone has additions to suggest, please send
me mail.
- Jonathan
\begin{thebibliography}{99}
\bibitem{SICP}
Harold Abelson and Gerald Jay Sussman with Julie Sussman.
{\em Structure and Interpretation of Computer Programs.}
MIT Press, Cambridge, 1985.
\bibitem{Bartley86}
David H.~Bartley and John C.~Jensen.
The implementation of PC Scheme.
To appear in {\em Proceedings of the 1986 ACM Conference on Lisp
and Functional Programming}.
\bibitem{Scheme81}
John Batali, Edmund Goodhue, Chris Hanson, Howie Shrobe, Richard
M.~Stallman, and Gerald Jay Sussman.
The Scheme-81 architecture---system and chip.
In {\em Proceedings, Conference on Advanced Research in VLSI},
pages 69--77.
Paul Penfield, Jr., editor.
Artech House, 610 Washington Street, Dedham MA, 1982.
\bibitem{RRRS}
William Clinger, editor.
The revised revised report on Scheme, or an uncommon Lisp.
MIT Artificial Intelligence Memo 848, August 1985.
Also published as Computer Science Department Technical Report 174,
Indiana University, June 1985.
\bibitem{Clinger84}
William Clinger.
The Scheme 311 compiler: An exercise in denotational semantics.
In {\em Conference Record of the 1984 ACM Symposium on Lisp and
Functional Programming}, pages 356--364.
\bibitem{Dybvig86}
R.~Kent Dybvig, Daniel P.~Friedman, and Christopher T.~Haynes.
Expansion-passing style: Beyond conventional macros.
To appear in {\em Proceedings of the 1986 ACM Conference on Lisp and
Functional Programming.}
\bibitem{Eisenberg85}
Michael A.~Eisenberg.
Bochser: an integrated Scheme programming system.
MIT Laboratory for Computer Science Technical Report 349,
October 1985.
\bibitem{Feeley86}
Marc Feeley.
Deux approches \`{a} l'implantation du language Scheme.
M.Sc.~thesis, Department of Computer Science and Operations Research,
University of Montreal, May 1986.
\bibitem{Felleisen86}
Matthias Felleisen, Daniel P.~Friedman, Eugene Kohlbecker, and Bruce Duba.
Reasoning with continuations.
In {\em Proceedings of the Symposium on Logic in Computer Science},
pages 131--141.
IEEE Computer Society Press, Washigton DC, 1986.
\bibitem{Scheme311}
Carol Fessenden, William Clinger, Daniel P.~Friedman, and Christopher Haynes.
Scheme 311 version 4 reference manual.
Indiana University Computer Science Technical Report 137, February 1983.
\bibitem{Scheme84}
D.~Friedman, C.~Haynes, E.~Kohlbecker, and M.~Wand.
Scheme 84 interim reference manual.
Indiana University Computer Science Technical Report 153, January 1985.
\bibitem{Friedman85}
Daniel P.~Friedman and Christopher T.~Haynes.
Constraining control.
In {\em Proceedings of the Twelfth Annual Symposium on Principles of
Programming Languages}, pages 245--254.
ACM, January 1985.
\bibitem{Haynes84}
Christopher T.~Haynes, Daniel P.~Friedman, and Mitchell Wand.
Continuations and coroutines.
In {\em Conference Record of the 1984 ACM Symposium on Lisp and
Functional Programming,} pages 293--298.
\bibitem{Haynes86}
Christopher T.~Haynes.
Logic continuations.
In {\em Proceedings of the Third International Conference on
Logic Programming,\/} pages \todo{x--y}.
Springer-Verlag, July 1986.
% and to appear in {\it The Journal of Logic Programming.}
\bibitem{Engines}
Christopher T.~Haynes and Daniel P.~Friedman.
Engines build process abstracions.
In {\em Conference Record of the 1984 ACM Symposium on Lisp and
Functional Programming,\/} pages 18--24.
\bibitem{Henderson82}
Peter Henderson. Functional Geometry.
In {\em Conference Record of the 1982 ACM Symposium on Lisp and
Functional Programming}, pages 179--187.
\bibitem{Kohlbecker86}
Eugene Edmund Kohlbecker~Jr.
{\em Syntactic Extensions in the Programming Language Lisp.}
PhD thesis, Indiana University, August 1986.
\bibitem{Kranz86}
David Kranz, Richard Kelsey, Jonathan Rees, Paul Hudak, James Philbin,
and Norman Adams.
Orbit: An optimizing compiler for Scheme.
In {\em Proceedings of the SIGPLAN '86 Symposium on Compiler
Construction}, pages 219--233.
ACM, June 1986.
\bibitem{Landin65}
Peter Landin.
A correspondence between Algol 60 and Church's lambda notation: Part I.
{\em Communications of the ACM} 8(2):89--101, February 1965.
\bibitem{McDermott80}
Drew McDermott.
An efficient environment allocation scheme in an interpreter for a
lexically-scoped lisp.
In {\em Conference Record of the 1980 Lisp Conference,} pages
154--162.
The Lisp Conference, P.O.~Box 487, Redwood Estates CA,
August 1980.
\bibitem{MITScheme}
MIT Department of Electrical Engineering and Computer Science.
Scheme manual, seventh edition.
September 1984.
\bibitem{Muchnick80}
Steven S.~Muchnick and Uwe F.~Pleban.
A semantic comparison of Lisp and Scheme.
In {\em Conference Record of the 1980 Lisp Conference}, pages 56--64.
The Lisp Conference, August 1980.
\bibitem{Naur63}
Peter Naur et al.
Revised report on the algorithmic language Algol 60.
{\em Communications of the ACM} 6(1):1--17, January 1963.
\bibitem{Penfield81}
Paul Penfield, Jr.
Principal values and branch cuts in complex APL.
In {\em APL '81 Conference Proceedings,} pages 248--256.
ACM SIGAPL, San Francisco, September 1981.
Proceedings published as {\em APL Quote Quad} 12(1), ACM, September 1981.
\bibitem{Pitman83}
Kent M.~Pitman.
The revised MacLisp manual (saturday evening edition).
MIT Artificial Intelligence Laboratory Technical Report 295, May 1983.
\bibitem{Pitman80}
Kent M.~Pitman.
Special forms in Lisp.
In {\em Conference Record of the 1980 Lisp Conference}, pages 179--187.
The Lisp Conference, August 1980.
\bibitem{Rees82}
Jonathan A.~Rees and Norman I.~Adams IV.
T: A dialect of Lisp or, lambda: The ultimate software tool.
In {\em Conference Record of the 1982 ACM Symposium on Lisp and
Functional Programming}, pages 114--122.
\bibitem{Rees84}
Jonathan A.~Rees, Norman I.~Adams IV, and James R.~Meehan.
The T manual, fourth edition.
Yale University Computer Science Department, January 1984.
\bibitem{Reynolds72}
John Reynolds.
Definitional interpreters for higher order programming languages.
In {\em ACM Conference Proceedings}, pages 717--740.
ACM, \todo{month?}~1972.
\bibitem{Rozas84}
Guillermo J.~Rozas.
Liar, an Algol-like compiler for Scheme.
S.~B.~thesis, MIT Department of Electrical Engineering and Computer
Science, January 1984.
\bibitem{Smith84}
Brian C.~Smith.
Reflection and semantics in a procedural language.
MIT Laboratory for Computer Science Technical Report 272, January 1982.
\bibitem{Stallman80}
Richard M.~Stallman.
Phantom stacks---if you look too hard, they aren't there.
MIT Artificial Intelligence Memo 556, July 1980.
\bibitem{Imperative}
Guy Lewis Steele Jr.~and Gerald Jay Sussman.
Lambda, the ultimate imperative.
MIT Artificial Intelligence Memo 353, March 1976.
\bibitem{Declarative}
Guy Lewis Steele Jr.
Lambda, the ultimate declarative.
MIT Artificial Intelligence Memo 379, November 1976.
\bibitem{Debunking}
Guy Lewis Steele Jr.
Debunking the ``expensive procedure call'' myth, or procedure call
implementations considered harmful, or lambda, the ultimate GOTO.
In {\em ACM Conference Proceedings}, pages 153--162.
ACM, 1977.
\bibitem{Macaroni}
Guy Lewis Steele Jr.
Macaroni is better than spaghetti.
In {\em Proceedings of the Symposium on Artificial Intelligence and
Programming Languages}, pages 60--66.
These proceedings were published as a special joint issue of {\em
SIGPLAN Notices} 12(8) and {\em SIGART Newsletter} 64, August 1977.
\bibitem{Rabbit}
Guy Lewis Steele Jr.
Rabbit: a compiler for Scheme.
MIT Artificial Intelligence Laboratory Technical Report 474, May 1978.
\bibitem{CLoverview}
Guy Lewis Steele Jr.
An overview of Common Lisp.
In {\em Conference Record of the 1982 ACM Symposium on Lisp and
Functional Programming}, pages 98--107.
\bibitem{CLtL}
Guy Lewis Steele, Jr.
{\em Common Lisp: The Language.}
Digital Press, Burlington MA, 1984.
\bibitem{Scheme78}
Guy Lewis Steele, Jr.~and Gerald Jay Sussman.
The revised report on Scheme, a dialect of Lisp.
MIT Artificial Intelligence Memo 452, January 1978.
\bibitem{TAOTI}
Guy Lewis Steele, Jr.~and Gerald Jay Sussman.
The art of the interpreter, or the modularity complex (parts zero, one,
and two).
MIT Artificial Intelligence Memo 453, May 1978.
\bibitem{DOALBP}
Guy Lewis Steele, Jr.~and Gerald Jay Sussman.
Design of a Lisp-based processor.
{\em Communications of the ACM} 23(11):628--645, November 1980.
\bibitem{Dream}
Guy Lewis Steele, Jr.~and Gerald Jay Sussman.
The dream of a lifetime: a lazy variable extent mechanism.
In {\em Conference Record of the 1980 Lisp Conference}, pages 163--172.
The Lisp Conference, August 1980.
\bibitem{Scheme75}
Gerald Jay Sussman and Guy Lewis Steele, Jr.
Scheme: an interpreter for extended lambda calculus.
MIT Artificial Intelligence Memo 349, December 1975.
\bibitem{Scheme79}
Gerald Jay Sussman, Jack Holloway, Guy Lewis Steele, Jr., and Alan Bell.
Scheme-79---Lisp on a chip.
{\em IEEE Computer} 14(7):10--21, July 1981.
\bibitem{Stoy77}
Joseph E.~Stoy.
{\em Denotational Semantics: The Scott-Strachey Approach to
Programming Language Theory.}
MIT Press, Cambridge, 1977.
\bibitem{TI85}
Texas Instruments, Inc.
{\em TI Scheme Language Reference Manual.}
Preliminary version 1.0, November 1985.
\bibitem{Wand78}
Mitchell Wand.
Continuation-based program transformation strategies.
{\em Journal of the ACM} 27(1):174--180, 1978.
\bibitem{Wand80}
Mitchell Wand.
Continuation-based multiprocessing.
In {\em Conference Re\-cord of the 1980 Lisp Conference}, pages 19--28.
The Lisp Conference, August 1980.
\end{thebibliography}
∂21-Jul-86 1325 @MC.LCS.MIT.EDU:gls@Think.COM Re: Scheme's DO construct
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Date: Mon, 21 Jul 86 15:13 EDT
From: Guy Steele <gls@Think.COM>
Subject: Re: Scheme's DO construct
To: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA, rrrs-authors@MC.LCS.MIT.EDU
Cc: gls@AQUINAS
In-Reply-To: <8607152252.AA19578@tekchips.TEK>
Message-Id: <860721151311.0.GLS@BOETHIUS.THINK.COM>
Date: 15 Jul 86 15:52:52 PDT (Tue)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
...
It seems to me that if we truly want to discourage people from writing
functional programs, a more effective way to do it would be to change
Scheme so people can't program in the functional style until they master
a set of arbitrarily chosen rules for inserting tokens like #' and FUNCALL
into their programs.
Heh, heh, heh. Well put, Will!
--Guy
∂21-Jul-86 1357 @MC.LCS.MIT.EDU:YEKTA@AI.AI.MIT.EDU Bobcat scheme
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Date: Mon, 21 Jul 86 16:37:10 EDT
From: Yekta Gursel <YEKTA@AI.AI.MIT.EDU>
Subject: Bobcat scheme
To: bc@MEDIA-LAB.MIT.EDU
cc: scheme@MC.LCS.MIT.EDU
In-reply-to: Msg of Mon 21 Jul 86 14:38:21 EDT from William H Coderre <bc at MEDIA-LAB.MIT.EDU>
Message-ID: <[AI.AI.MIT.EDU].73422.860721.YEKTA>
Just say "scheme -heap nnn" where "nnn" is the number of kilo-items...
I think the default is 150 and I have run programs with heaps as high as 1200.
(You should have enough swap space for that if you are planning run at that
heap value).
Best, Yekta
∂22-Jul-86 0710 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU title wars
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Date: Tue, 22 Jul 86 10:10:29 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: title wars
To: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].73688.860722.JAR>
The title I chose for the report is under siege. I guess this means we
need to discuss what it should be. I think the complaint is that the
superscript will pose typesetting and pronunciation problems for people
who cite the report. But think of the hundreds of papers with "SL←2(R)"
in their title. Oh well.
The main thing that's important to me is that it be as similar as
possible to "Revised Report on the Algorithmic Language ALGOL 60".
Beyond that I don't much care. Here are other possibilities:
- Dan Friedman has suggested "Revised Report on the Algorithmic Language
SCHEME" but this could be confused much too easily with the "Revised
Report on Scheme".
- "Another Report on the Algorithmic Language SCHEME"
(suggestive of YACC.) I sort of like this one.
- "A Report on the Algorithmic Language SCHEME"
- "Thrice Revised Report on the Algorithmic Language SCHEME"
This raises fomatting problems, since without the "thrice" it's
already as wide as it can be without deviating from the Algol report
layout.
- "Fourth Report on the Algorithmic Language SCHEME"
This has the advantage that it makes the next version easier to name.
"Report #4 on...", "The Next Report on ..." [imitative of "the
next whole earth catalog"], ...
or we could give the language a new name? no.
∂22-Jul-86 0717 @MC.LCS.MIT.EDU:HAL%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU title wars
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Date: Tue, 22 Jul 1986 10:16 EDT
Message-ID: <HAL.12224716985.BABYL@MIT-OZ>
From: HAL%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU
To: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Cc: rrrs-authors@MC.LCS.MIT.EDU
Subject: title wars
In-reply-to: Msg of 22 Jul 1986 10:10-EDT from Jonathan A Rees <JAR at AI.AI.MIT.EDU>
i like the title as it is.
∂22-Jul-86 1143 @MC.LCS.MIT.EDU:CPH@AI.AI.MIT.EDU title wars
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Date: Tue, 22 Jul 86 14:08:30 EDT
From: Chris Hanson <CPH@AI.AI.MIT.EDU>
Subject: title wars
To: JAR@AI.AI.MIT.EDU
cc: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Tue 22 Jul 86 10:10:29 EDT from Jonathan A Rees <JAR at AI.AI.MIT.EDU>
Message-ID: <[AI.AI.MIT.EDU].73801.860722.CPH>
A minor note: I'd prefer that the word "Scheme" not be upper-cased in
the report. While this is appropriate for an acronym like "ALGOL", it
does not seem to be for "Scheme", which is not an abbreviation for
anything.
I don't really feel strongly about this, I just thought I would point
it out.
BTW, if we *must* change the title, I vote for "Fourth Report...".
∂22-Jul-86 1157 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU title wars
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Date: Tue, 22 Jul 86 14:57:41 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: title wars
To: CPH@AI.AI.MIT.EDU
cc: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Tue 22 Jul 86 14:08:30 EDT from Chris Hanson <CPH at AI.AI.MIT.EDU>
Message-ID: <[AI.AI.MIT.EDU].73822.860722.JAR>
Date: Tue, 22 Jul 86 14:08:30 EDT
From: Chris Hanson <CPH at AI.AI.MIT.EDU>
A minor note: I'd prefer that the word "Scheme" not be upper-cased in
the report. While this is appropriate for an acronym like "ALGOL", it
does not seem to be for "Scheme", which is not an abbreviation for
anything.
Rationale:
I agree that "Scheme" generally shouldn't generally be in upper case,
and I think that it's "Scheme" everywhere else in the report. However,
I wanted to capitalize it in the title because this helps make it look
like the Algol 60 report.
∂22-Jul-86 1243 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: title wars
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Date: Tue 22 Jul 86 13:32:20-CDT
From: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: Re: title wars
To: JAR%ai.ai.mit.edu@CSNET-RELAY.ARPA,
rrrs-authors%mc.lcs.mit.edu@CSNET-RELAY.ARPA
Cc: Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
In-Reply-To: <[AI.AI.MIT.EDU].73688.860722.JAR>
Message-Id: <12224763647.36.BARTLEY@CSC60>
I have no real problem with leaving the title the way it is. Another
alternative would be ``1986 Revised Report ...''.
David Bartley
-------
∂22-Jul-86 1252 @MC.LCS.MIT.EDU,@YALE-BULLDOG.ARPA:hudak@YALE.ARPA Re: Performance and Evaluation of Scheme Systems...
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From: Paul Hudak <hudak@YALE.ARPA>
Message-Id: <8607221913.AA06470@Yale-Bulldog.YALE.ARPA>
Subject: Re: Performance and Evaluation of Scheme Systems...
To: Mike Wilson <Mike←Wilson%CARLETON.BITNET@WISCVM.WISC.EDU>
Cc: scheme%mc.lcs.mit.edu@CSNET-RELAY.ARPA
In-Reply-To: Mike Wilson <Mike←Wilson%CARLETON.BITNET@WISCVM.WISC.EDU>, 21 Jul 86 08:04:00 EDT
I've just been looking through the book ←Performance and Evaluation
of Lisp Systems← (Richard P. Gabriel, The MIT Press). It's got benchmark
results for several simple programs run on the more common lisp systems.
Has anyone run these tests in CScheme/MacScheme/TIScheme? It would be
interesting to see how we stack up. (I have to admit I am *impressed*
with their times for the IBM 3081 and CRAY-XMP. Oh well...)
The following is an excerpt from the paper:
Kranz, D., Kelsey, R., Rees, J., Hudak, P., Philbin, J., and Adams, N.
"ORBIT: an optimizing compiler for Scheme" in Proceedings of ACM
SIGPLAN '86 Symposium on Compiler Construction, June 1986, pp. 219-233.
Also to be published as SIGPLAN Notices Vol. 21, No. 7, July 1986.
Orbit vs. Other Lisp Engines:
Orbit 3600 Dorado 8600 780
Program (SUN III) +IFU (Dec CL) (Dec CL)
-------------------------------------------------------
Tak 0.25 0.43 0.52 0.45 1.83
Takl 1.63 4.95 3.62 2.03 7.34
Boyer 15.84 9.40 17.08 12.18 46.79
Browse 40.28 21.43 52.50 38.69 118.51
Destructive 1.24 2.18 3.77 2.10 6.38
Deriv 3.62 3.79 15.70 4.27 13.76
Dderiv 4.92 3.89 17.70 6.58 19.00
IDiv2 0.24 1.51 3.43 1.65 5.00
RDiv2 0.36 2.50 4.08 2.52 9.84
Triangle 84.36 116.99 252.20 99.73 360.85
Fprint 2.18 2.60 2.93 1.08 3.94
Fread 2.62 4.60 1.57 2.34 7.24
Tprint 1.66 4.89 5.55 0.70 2.85
Orbit vs. PSL vs. Franz:
Orbit PSL Franz
Program DN300 DN300 Sun II
-------------------------------------
Tak 1.34 1.62 2.37
Takl 6.21 12.90 12.82
Boyer 63.16 46.92 37.94
Destructive 7.91 10.16 9.57
Dderiv 28.12 28.95 16.95
Orbit vs. Algol-like Languages:
DEC DEC
Program Orbit Unix C DEC C Pascal Modula II
---------------------------------------------------
Perm 1.26 2.6 2.5 2.5 2.0
Tower 1.65 2.6 2.7 2.6 1.9
ORBIT was built (primarily) at Yale, and its availability will be
announced at the upcoming LISP Conference. If you want more details
about ORBIT or the benchmarks, please read the above cited paper.
-Paul
∂22-Jul-86 1529 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: title wars
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Date: Tue 22 Jul 86 15:37:57-CDT
From: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: Re: title wars
To: JAR%ai.ai.mit.edu@CSNET-RELAY.ARPA, CPH%ai.ai.mit.edu@CSNET-RELAY.ARPA
Cc: rrrs-authors%mc.lcs.mit.edu@CSNET-RELAY.ARPA,
Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
In-Reply-To: <[AI.AI.MIT.EDU].73822.860722.JAR>
Message-Id: <12224786515.36.BARTLEY@CSC60>
Date: Tue, 22 Jul 86 14:57:41 EDT
From: Jonathan A Rees <JAR%ai.ai.mit.edu@CSNET-RELAY.ARPA>
Date: Tue, 22 Jul 86 14:08:30 EDT
From: Chris Hanson <CPH at AI.AI.MIT.EDU>
A minor note: I'd prefer that the word "Scheme" not be upper-cased in
the report. While this is appropriate for an acronym like "ALGOL", it
does not seem to be for "Scheme", which is not an abbreviation for
anything.
Rationale:
I agree that "Scheme" generally shouldn't generally be in upper case,
and I think that it's "Scheme" everywhere else in the report. However,
I wanted to capitalize it in the title because this helps make it look
like the Algol 60 report.
I agree with Chris -- Scheme is a word, not an acronym. ALGOL is an
acronym and should be written in all caps. If you want it to look EXACTLY
like the Algol 60 report, name the language ALGOL!
David Bartley
-------
∂22-Jul-86 1755 @MC.LCS.MIT.EDU:GJS%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU title
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Date: Tue 22 Jul 86 20:41:50-EDT
From: "Gerald Jay Sussman" <GJS%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>
Subject: title
To: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <12224830912.34.GJS@OZ.AI.MIT.EDU>
I think that the current title -- R↑4 and all -- is really nice.
-------
∂24-Jul-86 1244 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU call-with-xput-port vs. call-with-xput-file
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Date: Thu, 24 Jul 86 15:12 EDT
From: Jonathan A Rees <JAR@MIT-AI.ARPA>
Subject: call-with-xput-port vs. call-with-xput-file
To: rrrs-authors@MIT-MC.ARPA
Message-ID: <860724151248.1.JAR@ROCKY-GRAZIANO.LCS.MIT.EDU>
Date: Mon, 14 Jul 86 11:47:21 est
From: Kent Dybvig <dyb%iuvax.indiana.edu@CSNET-RELAY.ARPA>
To: rrrs-authors%mit-mc.CSNET@CSNET-RELAY.ARPA
Subject: call-with-xput-port vs. call-with-xput-file
I favor changing call-with-input-file and call-with-output-file to
call-with-input-port and call-with-output-port. However, I have some
questions related to the change and to ports in general.
1. I saw lots of confusion over the fact that you open a file (with
open-input-file and open-output-file) but close a port (with close-
input-port and close-output-port). Changing the "call-with" names
could increase the confusion. Should we change open-input-file and
open-output-file to open-input-port and open-output-port?
2. I have added string ports to Chez Scheme and need to choose names.
If we have call-with-...-file and open-...-file, I can introduce the
names call-with-...-string and open-...-string. On the other hand,
if we have call-with-...-port and open-...-port, I can introduce the
names call-with-...-string-port and open-...-string-port. The names
are longer but perhaps more descriptive. How do these names sound?
The point of this question is that any names we choose should
generalize to other types of ports.
I see these two points (together with general conservatism) as arguments
AGAINST changing the names. I am now inclined not to make the change.
5. Why is call-with-input-file essential and open-input-file not?
This resulted from a general spirit of minimalism at the Brandeis
meeting. The first is sufficient while the second isn't. Personally, I
never use the second.
If call-with-input-file is analogous to
call-with-current-continuation, why do we not have
(call-with-new-string <length> <proc>) instead of make-string or
(call-with-pair <obj1> <obj2> <proc>) instead of cons, etc? Because
call-with-current-continuation is special---a function
make-continuation would be problematic. In short, while I see the
merit in with-input-from-file since it closes the file and rebinds a
standard port, I cannot see the merit in call-with-input-file.
The merit is that it makes certain that the port gets closed. If we had to
deallocate resources and locks associated with allocated objects like strings,
then I think it would be a good idea to have call-with things for
those too.
Jonathan.
∂25-Jul-86 0022 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA Re: July 15 draft sent
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Date: Fri 25 Jul 86 00:35:05-CDT
From: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: Re: July 15 draft sent
To: JAR%ai.ai.mit.edu@CSNET-RELAY.ARPA,
rrrs-authors%mc.lcs.mit.edu@CSNET-RELAY.ARPA
Cc: Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
In-Reply-To: <[AI.AI.MIT.EDU].71397.860716.JAR>
Message-Id: <12225408585.58.BARTLEY@CSC60>
I probably won't start another pass over it until a week from tomorrow
(i.e. the 17th), so don't feel guilty if you don't send your remarks to
me before that. After the 20th is when you can start feeling guilty.
I received my copy of the new revision to the R↑3RS yesterday (July 23)
and enclose my detailed comments below (boy, do I feel guilty!). I am
quite impressed overall with the current state of the document and want to
commend Jonathan for the success of his efforts! Nearly all of my
objections to the previous draft have been resolved satisfactorily. I
will repeat below some that have not, but in general I am content to leave
their resolution in JAR's hands.
[page 1]
I prefer to change "SCHEME" in the title to "Scheme", since it is not an
acronym.
[page 3]
I prefer to change "Snobol" to "SNOBOL", since it IS an acronym.
[page 4]
[line 4, left col] Change "if the feature is not AS essential feature"
to "if the feature is not AN essential feature".
[line 21, left col] Change "for a call to the procedures" (plural) to
"for a call to the procedure" (singular).
[line 29, left col] Change "indicates that THE in" to "indicates that, in".
[first bullet under 2.1] Remove the comma after "Certain identifiers".
[page 5]
[first paragraph of 2.2] Whitespace may also occur in the space
character (denoted by "#\ ").
[near the end of 2.3] You say that #T and #F are boolean CONSTANTs and
that #\ introduces a character CONSTANT; shouldn't you say that #(
introduces a vector CONSTANT also?
[last 2 lines of 2.3] If my proposed number syntax is adopted, #S and #L
will not exist.
[last 2 lines, right col] Flush the "Note: ..."; I assume it is a note
to yourself (?).
[page 6]
[section 3.2] Change "#fand" to "#f and".
[paragraph 6, sec 3.2] Change "Note that THAT the" to "Note that the".
[page 7]
[last paragraph of sec. 4.1.3] Change "Note also that in many
dialects..." to "{\em Note:} In many dialects...".
[page 8]
[line 6, right col] Shouldn't the notation (<test> => <recipient>) be
listed as a non-essential syntax in the heading rather than buried as an
implementation note in the body of the text?
[last paragraph, right col] I was very happy with your use of {\em
Syntax:} and {\em Semantics:} headers but they disappeared from AND
onward. I guess you ran out of time...
[page 9]
[first paragragh, sec 4.2.2] There is a mysterious whitespace at the
beginning of the fourth line of the paragragh.
[description of LET*] Shouldn't you replicate the description of
<bindings> and <body>? You do for LETREC.
Try to avoid the "widow" line for the heading of LET*.
[last line, right col] Here, and elsewhere, you have incomplete sentences
in which the subject is missing. This doesn't particularly offend me, and
it seems to read well, so I see no reason to correct it right away...
[page 10]
[end of 4.2.4] The indenting for the "(LET LOOP ((NUMBERS ..." example
has gone awry.
[page 12]
[end of 6.1] I'd like to see the example (EQ? NIL 'NIL) ==> #F added.
This reinforces the wording in the last paragraph of the left column,
which might be missed by someone looking only at the definition of NIL.
[page 14]
[last paragraph of the description of EQ?] Omit the words "instead of as
a subroutine call". It seems to imply that anything other than a pointer
comparison must be performed out of line, or that a pointer comparison
would necessarily be performed in line.
[page 17]
[lines 10, 11 of left col] Omit the sentence: "It is questionable
whether these features [slashification and uninterned symbols] are worth
their complexity, so they are not standard in Scheme." This editorial
comment is unnecessary and invites the response: "Then why is
SYMBOL->STRING worth while?"
[page 22]
[sec 6.6] Clarify the sentence: "This rule resolves the ambiguous case
... the space character AS AS the ...".
[page 30]
[sec 7.1.2, syntax of numbers] I mailed out a proposal for a syntax of
numbers compatible with Common Lisp last week but haven't received any
feedback. Did it fail to make it to the mailing list or is it that
non-controversial?
[page 36]
Try to avoid the "widow" line for the subtitle "EXAMPLE".
[Index]
Add #T and #F, and possibly #!TRUE and #!FALSE (page 12), to the index.
Regards,
David Bartley
-------
∂25-Jul-86 1026 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: number syntax
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To: Bartley%TI-CSL.CSNET@CSNET-RELAY.ARPA
Cc: JAR@AI.AI.MIT.EDU, rrrs-authors@MC.LCS.MIT.EDU
Subject: Re: number syntax
In-Reply-To: Your message of Wed 16 Jul 86 10:53:32-CDT.
<12223161873.35.BARTLEY@CSC60>
Date: 23 Jul 86 11:51:22 PDT (Wed)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
After studying the recent proposal by David Bartley and Mark Meyer, I'm
afraid I have to object to using it in the report. I probably just don't
understand it, and I might change my mind if they'll explain it to me
better. I don't have much problem with the syntactic changes they propose.
The main problem I have with their proposal is that it addresses the syntax,
which I don't much care about, but doesn't address the semantic properties
like exactness and integer-ness. I have repeated most of their proposal
(indented two spaces) in order to point out the parts I object to.
(4) CL provides only the #C(real real) notation for complex numbers; R↑3RS
provides infix notations for both polar and rectangular forms. For
compatibility with CL, R↑3RS should support the #C notation and the infix
forms should be non-essential extensions.
Shouldn't the #C syntax be inessential also, since integer-only
implementations are allowed? Shouldn't all productions with decimal
points or slashes be inessential as well?
(5) CL integers may optionally terminate in a decimal point; R↑3RS permits
such a number to be treated as floating point and it is debated whether it
is to be considered exact. This is a serious problem, since many
procedures are defined to accept only integer values. Is the call
(INTEGER->CHAR 55.) valid? We propose that this be a non-essential
feature in R↑3RS.
It seems to me that most procedures that are currently defined to accept
only integer values should have been defined to accept only exact integer
values. Our concept of an integer needs to be tightened up. I propose
that INTEGER? be defined to be compatible with
(define integer?
(lambda (x)
(and (real? x) (= x (truncate x)))))
With a definition such as this it seems likely that 55. will be an integer.
The real question is whether it is exact. I haven't been able to answer
that question on the basis of the proposal.
We propose the following syntax for numbers in Scheme. (Recall that
letter case is insignificant in the grammar and that the rules for <ureal
R>, <prefix R>, etc., should be replicated for R = 2, 8, 10, and 16.)
<number> --> <real> | #c( <real> <real> )
<real> --> <prefix R> <sign> <ureal R>
<prefix R> --> <exactness> <radix R>
<exactness> --> <empty> | #i | #e
<radix 2> --> #b
<radix 8> --> #o
<radix 10> --> <empty> | #d
<radix 16> --> #x
<sign> --> <empty> | + | -
<ureal R> --> <integer R> | <ratio R> | <flonum R>
<integer R> --> <digit R>+ #*
<ratio R> --> <digit R>+ #* / <digit R>+ #*
<flonum R> --> . <digit R>+ #* <expon>
| <digit R>+ . <digit R>* #* <expon>
| <digit R>+ #* . #* <expon>
<expon> --> <empty> | <expon-marker> <sign> <digit>+
I believe the <digit>+ in the above production was intended to be
<digit 10>+.
<expon-marker> --> e | f | d | l | s
<digit 2> --> 0 | 1
<digit 8> --> 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7
<digit 10> --> <digit 8> | 8 | 9
<digit 16> --> <digit 10> | a | b | c | d | e | f
Although we have incorporated <exactness> and the use of `#' above, they
should be stated to be non-essential features of Scheme.
Nonessential feature: integers with optional decimal points.
<integer R> --> <digit R>+ #* .
This production is redundant, since all the strings it generates are
generated by the third production for <flonum R>. I judge by this
and other redundancies that the name of the non-terminal is intended
to carry semantic freight, but I can't tell what semantics is intended.
This is my fundamental objection to the proposal: it is a syntax
without a semantics.
Nonessential feature: integers and ratios with exponents.
<integer R> --> <digit R>+ #* <expon>
<ratio R> --> <digit R>+ #* <expon> / <digit R>+ #* <expon>
Similarly the production above for <integer R> is redundant, since it is
exactly the same as the first production for <flonum R>.
Nonessential number productions representing complex numbers. We worry
that the forms <real>+<ureal>i and <real>-<ureal>i can be hard to parse.
Perhaps combining the suffix `i' with the infix `+' or `-' would be
palatable to those who want this feature.
<number> --> <real> +i <ureal>
| <real> -i <ureal>
| <real> @ <real>
I'm not sure that this syntax is any easier to parse than the old syntax,
but it isn't any worse.
Regards,
David Bartley
Mark Meyer
-------
Peace, Will Clinger
∂25-Jul-86 1127 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU (eqv? #e1 #i1)
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From: Jonathan A Rees <JAR@MIT-AI.ARPA>
Subject: (eqv? #e1 #i1)
To: rrrs-authors@MIT-MC.ARPA
Message-ID: <860725142516.4.JAR@ROCKY-GRAZIANO.LCS.MIT.EDU>
Date: 22 Jul 86 11:31:02 PDT (Tue)
From: willc%tekchips.tek.csnet at CSNET-RELAY.ARPA
Technical question relating to exactness: Are 1 and 1.0 operationally
equivalent? (That is, if we wind up adopting the proposal that 1 be
read as an exact integer while 1.0 is read as an inexact integer, then
(EQV? 1 1.0) must be false. This is incompatible with the RRRS, which
says that EQV? returns true when its arguments are numbers that are
equal according to the = procedure. This incompatibility is not listed
in the notes on page 35. I wonder if the incompatibility was recognized
and intended.)
I assumed that this detail was an unintentional omission from RRRS.
Clearly #e1 and #i1 are distinguishable. I'll list this in the notes
section.
- Jonathan
∂25-Jul-86 1346 @MC.LCS.MIT.EDU:ramsdell%linus@mitre-bedford.ARPA July 15th draft
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Subject: July 15th draft
On title wars, I am reminded of Norman's comments:
Scheme is fun and happy, and a bit quirky -- or are CDR and CAR and so many
relatives the ideal names for those procedures? Scheme is as serious as
LAMBDA, but as casual as CAR. Alas, what has become of dear PROGN? The
names are arbitrary and incidental; CAR and CDR remind us. Scheme is as
much an approach as a detailed concrete specification. But to be taken
seriously, for Scheme to be widely used, we must have the details and
concretions; they are essential but unimportant.
While publishers will most likely want to put out contracts on the
typing fingers of those who perpetrated the weird title, I think we
should have a little fun and keep the superscript in the title.
However, I do like the idea of NOT using all caps for Scheme in the
title.
David Bartley suggests changing "Snobol" into "SNOBOL" because it is
an acronym. If we do that, shouldn't we change "Algol" into "ALGOL"
and "Lisp" into "LISP"?
1) [Page 2, col 1, line 3] I am worried about the phrase "with
absolutely no restrictions on how they are composed". Certainly, the
expressions "1" and "2" should not be composed as "(1 2)". Doesn't
Scheme show that a small number of rules for forming expression
combined with a simple, uniform method of combining the expressions,
suffices to form a practical and efficient programming language?
2) [Page 5, col 1, paragraph 2] Too many parentheses. Only the first
pair are needed. Use commas for the others.
3) [Page 3, col 1, paragraph 3] Too many parentheses.
4) [Page 6, col 1, paragraph 1] From my reading of the paragraph, I
conclude that Common Lisp has no dynamic variables. After all, it
says that "To each place where a variable is bound in a program there
corresponds a region of the program text within which the binding is
effective." The lack of dynamic variables distinguishes Scheme from
Common Lisp and makes the above statement true.
5) [Page 10, col 1, line -16] Odd space between the words "region" and
"of".
6) [Page 10, col 2, line 1] Change to "general looping construct than
do, and may also be used to express recursive procedures."
7) [Page 14, col 1, line 22] The previous page states that there is
only one empty string. Therefore, (eqv? "" "") => #t, which implies
that (eq? "" "") => #t. If I am wrong, what does the statement about
the existence of one empty string mean?
8) [Page 27, col 2] I will simply say that, in my opinion,
call-with-xxput-port gives a user a better idea of what is going on,
as compared to call-with-xxput-file. In the interest of harmony, I
will rest my case unless I hear support from others.
John
∂26-Jul-86 2137 @MC.LCS.MIT.EDU:cth%iuvax.indiana.edu@CSNET-RELAY.ARPA corrections and suggestions
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From: Chris Haynes <cth%iuvax.indiana.edu@CSNET-RELAY.ARPA>
To: rrrs-authors%mit-mc.CSNET@CSNET-RELAY.ARPA
Subject: corrections and suggestions
I prefer "A Report ..." or "Fourth Report ...". In any case, remove
the bit about the ↑3 not being a footnote. No one is apt to mistake
the title's ↑3, for it is big and bold. It is *references* to the title
in other publications where the ↑3 will cause confusion, and the note
in the report won't do any good then.
I prefer "C.T. Haynes" in the author list, and "Christopher Haynes" in the
Background (p. 2).
In the summary, delete "and very few different ways to form expressions",
which is unnecessary and questionable.
p. 2: make those features --> make additional features
first real programming language -->
first widely used programming language
sub-dialects --> dialects
, while many others remain to be adopted. --> .
With Kent Dybvig, I would prefer that : not be an extended
alphabetic character, but be reserved for special uses.
2.3. unspecified future uses --> possible extensions in
discussion of [ ] and { }.
3.1. may name --> names
Question: Why say "A variable that does so is said to be bound to the
location." Is it possible to have variables that aren't bound to
locations? If so, how? The reader should not be kept in the dark.
Delete "Note: internale definitions not mentioned here."
3.2. #fand --> #f and
4.1 and 4.2. The "Syntax:" and "Semantics:" paragraph flags are
nice, but are not used after "case" (p. 8). I suggest flushing them.
Better to be consistent, and they aren't necessary for understanding.
4.2.4. Some implementations of Scheme permit a ... --> This ...
pretty printing of (let loop ...) is messed up.
5.1. consists a sequence --> consists of a sequence
6.2. if applying a mutation procedure to one causes the other to
change as well.
-->
if they have operationally equivalent values in corresponding
positions and applying a mutation procedure to one causes the
other to change as well.
For example, two pairs are equivalent if a set-car! operation on
one changes the car field of the other.
-->
For example, two pairs are not equivalent if a set-car!
operation on one does not change the car field of the other.
Questions: is "side-effect" defined anywhere? (A referee
recently critisized me for not defining it.)
6.4. (in the sense of eqv?) --> (in the sense of eq?)
[[the reader should be encouraged to think eq? on symbols]]
6.9, p. 27. is an ordinary Scheme procedure --> is a Scheme procedure
The classic use --> A common use
flush "when programmers need to do something fancy,"
I don't like the last sentence of 6.9. Opinions also differ on the
merits of SEQUENCE, but we didn't apologize for it or give SEQUENCE
less than optional status by not listing it under BEGIN as an
(optional) form. List CALL/CC as a procedure under
CALL-WITH-CURRENT-CONTINUATION and replace the last sentence with a
statement that CALL/CC is equivalent. Several of us feel rather
strongly about this.
6.10.1. I also prefer CALL-WITH-*-PORT and OPEN-*-PORT.
Replace the last sentence of the WITH-*-*-FILE paragraph with
"Furthermore, when these procedures return, they close the
default port and restore the previous default. If an escape procedure
is used to escape from the continuation of these procedures, their
behavior is implementation dependent."
[[Rational: the existing "in constrast" statement is incorrect.
Where is the contrast? And more important, some systems will
automatically change the default port if the continuation is escaped,
but we probably don't want to even mention, let alone require, such
behavior.]]
6.10.4. Delete the LOAD rational. The LOAD description expressly
says that expressions and definitions are read, so any uses of LOAD to
load such things as compiled files are implementation extensions anyway.
Delete the TRANSCRIPT-* Note. We haven't provided elementary tips
to implementers anywhere else.
BIBLIOGRAPHY: add the following
Daniel P. Friedman, Christopher T. Haynes, and Eugene Kohlbecker,
Programming with continuations. {\it In Programming Transformation and
Programming Environments,\/} P. Pepper (Ed.), pages 263--274,
Springer-Verlag, 1984.
The Report reads quite well now, and has come a long way in the last
few months. Thanks for all your efforts, Jonathan.
Chris Haynes
∂28-Jul-86 0810 @MC.LCS.MIT.EDU:ramsdell%linus@mitre-bedford.ARPA Fault logic in eq? comment
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Subject: Fault logic in eq? comment
Opps! I used faulty logic in:
7) [Page 14, col 1, line 22] The previous page states that there is
only one empty string. Therefore, (eqv? "" "") => #t, which implies
that (eq? "" "") => #t. If I am wrong, what does the statement about
the existence of one empty string mean?
Please ignore it!
[Page 27, col 2] I think there is support for changing
call-with-xxput-file to call-with-xxput-port. I am not convinced that
open-xxput-port is any better than open-xxput-file, the latter
expresses what the function does just as well as the former does.
[Page 2] While the introduction implies Scheme has no dynamic
variables and no separate name spaces for global values and functions,
maybe that difference with existing Lisps should be made more
explicit. Thus, after "... in the same way as an operand position."
one might add "In contrast, many other dialects of Lisp associate two
values with some variables, and the bindings in effect at run time may
depend on the run time history of a program --- not simply the static
program structure."
John
∂28-Jul-86 1616 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: corrections and suggestions
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Cc: rrrs-authors@MC.LCS.MIT.EDU
Subject: Re: corrections and suggestions
In-Reply-To: Your message of Thu, 24 Jul 86 17:21:19 est.
<8607270553.AA19279@tekchips.TEK>
Date: 28 Jul 86 09:54:02 PDT (Mon)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
3.1. may name --> names
Question: Why say "A variable that does so is said to be bound to the
location." Is it possible to have variables that aren't bound to
locations? If so, how? The reader should not be kept in the dark.
There exist identifiers that are not syntactic keywords. According to the
first sentence of 3.1, any such identifier may be used as a variable. The
catch comes in an implementation with unbound variables, such as PC Scheme,
where just using an identifier as a variable does not make it name a
location; that must be done with a binding construct. I see your point,
but I suspect that many readers would prefer to remain in the dark about
this sort of thing until the next paragraph.
A related issue is that (top level) DEFINE is missing from the list of
binding constructs in the next paragraph.
I don't like the last sentence of 6.9. Opinions also differ on the
merits of SEQUENCE, but we didn't apologize for it or give SEQUENCE
less than optional status by not listing it under BEGIN as an
(optional) form. List CALL/CC as a procedure under
CALL-WITH-CURRENT-CONTINUATION and replace the last sentence with a
statement that CALL/CC is equivalent. Several of us feel rather
strongly about this.
Whoa! Two wrongs don't make a right. Let's try to get rid of SEQUENCE
instead. Several of us feel rather strongly that CALL/CC ought to call
the C compiler. Seriously, to add alternative names for procedures now
would be inconsistent with our success in getting rid of =? et cetera.
Replace the last sentence of the WITH-*-*-FILE paragraph with
"Furthermore, when these procedures return, they close the
default port and restore the previous default. If an escape procedure
is used to escape from the continuation of these procedures, their
behavior is implementation dependent."
[[Rational: the existing "in constrast" statement is incorrect.
Where is the contrast? And more important, some systems will
automatically change the default port if the continuation is escaped,
but we probably don't want to even mention, let alone require, such
behavior.]]
The contrast is that WITH-*-*-FILE will close the default port whenever
you throw out of it without having done a CALL-WITH-CURRENT-CONTINUATION,
even if you stored the value of (CURRENT-*-PORT) in a global variable
before you did the throw. CALL-WITH-*-FILE would never do a thing like
that. To me, this is a striking contrast.
Peace, Will
∂29-Jul-86 1331 @MC.LCS.MIT.EDU:dyb@iuvax.indiana.edu critical problems with call---file, with---file
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Date: Tue, 29 Jul 86 02:10:41 est
From: "R. Kent Dybvig" <dyb@iuvax.indiana.edu>
To: rrrs-authors%mit-mc.CSNET@CSNET-RELAY.ARPA
Subject: critical problems with call---file, with---file
Cc: bartley%ti-csl.CSNET@CSNET-RELAY.ARPA, jar%mit-mc.CSNET@CSNET-RELAY.ARPA,
willc%tekchips@iuvax.indiana.edu
Regarding these quotes from the latest revision:
(under call-with-input-file, call-with-output-file)
If the procedure returns, then the port is closed
automatically and the value yielded by the procedure is
returned. If the procedure does not return, then Scheme
will not close the port unless it can prove that the
port will never again be used for a read or write operation.
(under with-input-from-file, with-output-to-file)
Furthermore, in contrast to call-with-input-file and
call-with-output-file, these procedures will arrange to
close the default port and restore the previous default
whenever the system can prove that the call to the
thunk will never return.
I have two problems with the wording of these two quotes. One of
these probems can be ignored, and we'll only have an ill-specified
and confusing set of procedures. The other cannot be ignored.
First, the one that cannot be ignored: From the wording of the
second quote, it is technically possible (and perhaps required!)
for a Scheme system to close a port out from under a procedure in
a way we do not intend. For example, if I write:
(with-input-from-file "foo.in"
(letrec ((loop (lambda ()
(write-char (read-char))
(loop))))
loop)),
it is clear that a clever Scheme system can prove that the thunk
will never return; however, it would be entirely inappropriate to
close the new default port and restore the old.
The second problem takes a little more explaining: I think that
most users will be very confused and rather upset that
call-with-input-file does not close the port automatically in the
case of a non-local exit, either programmed or through some sort
of error. Also, in the case of with---file, it is not clear
whether an implementation is required to close the port as soon as
it can prove that the call will never return, or sometime thereafter.
Furthermore, it is not clear how sophisticated the system must be
in proving this fact.
In the most recent version of Chez Scheme, ports are closed by the
storage manager once it determines there is no possibility of
reference. This will not necessarily occur as soon as the port
becomes inaccessible, but it is guaranteed that the system will not
run out of ports if there are any open, inaccessible ports around.
In addition, all ports are closed on exit from the system. This
is a much more general and reasonable solution to the problem of
closing ports than forcing the programmer to use confusing,
ill-defined procedures that don't necessarily help in the case
of non-local exits or errors.
It is fine to say that the port is closed when the procedure or thunk
returns, but we should flush the descriptions of what happens when
the procedure or thunk does not return, perhaps mentioning that, in
order to avoid running out of file-system resources, implementations
usually close ports it can prove are inaccessible. This would be
in the spirit of the earlier statement about not (usually!) running
out of storage (section 1.1, paragraph 4), and would also reinforce
the first-class status of ports.
Kent
p.s. We don't have much time, so please respond quickly.
∂29-Jul-86 1423 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU schedule
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Date: Tue, 29 Jul 86 16:35:08 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: schedule
To: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].77171.860729.JAR>
A version of the report is now at the printer. There will be a copy
in every Lisp conference registration packet.
As for SIGPLAN, I seem to have screwed up pretty badly; I thought that
having it done by early August would be good, since it would then get
into the October issue. However, I just found out from Wexelblat that
the October issue is proceedings for some conference. (This decision
was made rather late; the previous time I spoke with him, the October
issue was still open.) Therefore the earliest it can be out is the
November issue, and our new deadline is September 12.
For the Lisp conference version, I didn't do anything about number
syntax, since there seemed to be a bit of controversy remaining; also I
did nothing about the question of number input exactness, and didn't
rename the call-with-transput-pile procedures. What got printed was
rather close to the July 15 draft, incorporating, of course, most of the
corrections people sent me. Maybe we can fix these and other problems
by September, though.
Thanks to everyone who read the July 15 and other drafts so carefully.
If you won't be at the Lisp conference, let me know and I'll mail you a
copy of the latest thing.
Jonathan
∂29-Jul-86 1814 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Re: critical problems with call---file, with---file
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To: rrrs-authors@MC.LCS.MIT.EDU
Subject: Re: critical problems with call---file, with---file
Date: 29 Jul 86 15:26:46 PDT (Tue)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
...For example, if I write:
(with-input-from-file "foo.in"
(letrec ((loop (lambda ()
(write-char (read-char))
(loop))))
loop)),
it is clear that a clever Scheme system can prove that the thunk
will never return; however, it would be entirely inappropriate to
close the new default port and restore the old.
Nice example. Should we say instead that "If the procedure does not
return, Scheme will not close the port unless it can prove that the
continuation with which the procedure was called has become
inaccessible"?
I can't get very excited if ports aren't closed the instant they become
inaccessible, because I suspect that pairs aren't added to the free list
the instant they become inaccessible either. I can't see how it affects
my life.
As I read the report, implementations are not required to try to close
ports in the exceptional cases. Likewise, though implementations are
"permitted to reclaim the storage occupied by an object if they can
prove that the object cannot possibly matter to any future computation",
I don't see where implementations are actually required to reclaim
storage. I think it's clear that implementations are encouraged to do
both, and it's great that Chez Scheme is setting such a good example for
us to follow.
It would be reasonable to say that "in order to avoid running out of
file-system resources, implementations usually close ports it can
prove are inaccessible" if it were true. Is it?
Implementation note: In a very large multiprocessing implementation of
Scheme it might be more practical to remove limits on file-system
resources than to determine whether ports are accessible.
----------------------------------------------------------------
The section that describes differences between RRRS and R3RS should
note that (DEFINE (FOO ...) ...) is now equivalent to
(DEFINE FOO (LAMBDA (...) ...)) instead of to
(DEFINE FOO (REC FOO (LAMBDA (...) ...))).
Peace, Will
∂31-Jul-86 0732 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU rrrs authors meeting, lunch Tuesday
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Date: Thu, 31 Jul 86 09:52:31 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: rrrs authors meeting, lunch Tuesday
To: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Wed 30 Jul 86 17:01:20 PDT from Norman Adams <adams%tekchips.tek.csnet at CSNET-RELAY.ARPA>
Message-ID: <[AI.AI.MIT.EDU].77967.860731.JAR>
Date: Wed, 30 Jul 86 17:01:20 PDT
From: Norman Adams <adams%tekchips.tek.csnet at CSNET-RELAY.ARPA>
To: jar at AI.AI.MIT.EDU
It occurred to me that the bulk of the RRRS authoripods will be at
the lisp conference and that a meeting might bring quick resolution
to issues outstanding for the SIGPLAN edition of the R3RS. A
meeting might be fun even if there is nothing to resolve... What
say you? Perhaps there is not enough time to get a note out on
RRRS; maybe we could post something at the registration desk.
Good idea. What with Monday night being the banquet, and Tuesday night
being various Eulisp and Common Lisp meetings, I think lunchtime would
be best. Therefore I propose lunch on Tuesday, promptly following
cessation of the morning sessions.
If there's a major problem with this time then we can change it to lunch
Wednesday or some other time. I'll post something near the registration
desk in any case. See y'all there.
Jonathan
∂31-Jul-86 1111 @MC.LCS.MIT.EDU:fateman@DALI.BERKELEY.EDU Re: Performance and Evaluation of Scheme Systems...
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Date: Thu, 31 Jul 86 08:49:56 PDT
From: Richard Fateman <fateman@DALI.BERKELEY.EDU>
Message-Id: <8607311549.AA17087@dali.Berkeley.EDU>
To: Mike←Wilson%CARLETON.BITNET@WISCVM.WISC.EDU,
scheme%mc.lcs.mit.edu@CSNET-RELAY.ARPA
Subject: Re: Performance and Evaluation of Scheme Systems...
since the programs used for timing were allowed to be different from
the ones in RPG's book, (e.g. declarations) and at least some of the
programs are unrunnnable as given, the benchmark timings are somewhat
less useful than you might think. If YOU run them benchmarks on various
machines/lisps, you may get much different numbers.
∂04-Aug-86 0107 @MC.LCS.MIT.EDU:facility%cantuar.waterloo.edu@CSNET-RELAY.ARPA
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From: Facilities Committee <facility%cantuar.waterloo.edu@CSNET-RELAY.ARPA>
To: SCHEME <@CSNET-RELAY.ARPA,@watmath.waterloo.edu:SCHEME@MC.LCS.MIT.EDU>
Date: Thu, 31 Jul 86 10:44:24+1200
From: wolfgang@cantuar.Waterloo.edu (W. Kreutzer)
To: SCHEME@MIT-MC.csnet@watmath.Waterloo.edu
Subject: Chez Scheme
We would be interested in more info on Chez Scheme. Who can we contact ?
Since we are using an experimental connection from New Zealand, please
reply through either: wolfgang%cantuar@waterloo.csnet OR
...watmath!cantuar!wolfgang. Thanks. w.kreutzer Univ. of Canterbury, NZ
∂04-Aug-86 0158 @MC.LCS.MIT.EDU:facility%cantuar.waterloo.edu@CSNET-RELAY.ARPA
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From: Facilities Committee <facility%cantuar.waterloo.edu@CSNET-RELAY.ARPA>
To: SCHEME <@CSNET-RELAY.ARPA,@watmath.waterloo.edu:SCHEME@MC.LCS.MIT.EDU>
Date: Thu, 31 Jul 86 10:44:24+1200
From: wolfgang@cantuar.Waterloo.edu (W. Kreutzer)
To: SCHEME@MIT-MC.csnet@watmath.Waterloo.edu
Subject: Chez Scheme
We would be interested in more info on Chez Scheme. Who can we contact ?
Since we are using an experimental connection from New Zealand, please
reply through either: wolfgang%cantuar@waterloo.csnet OR
...watmath!cantuar!wolfgang. Thanks. w.kreutzer Univ. of Canterbury, NZ
∂06-Aug-86 0150 @MC.LCS.MIT.EDU:facility%cantuar.waterloo.edu@CSNET-RELAY.ARPA
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Date: Wed, 6 Aug 86 19:30:29 nzt
From: Facilities Committee <facility%cantuar.waterloo.edu@CSNET-RELAY.ARPA>
To: scheme <@CSNET-RELAY.ARPA,@watmath.waterloo.edu:scheme@MC.LCS.MIT.EDU>
Date: Thu, 31 Jul 86 10:44:24+1200
From: wolfgang@cantuar.Waterloo.edu (W. Kreutzer)
To: SCHEME@MIT-MC.csnet@watmath.Waterloo.edu
Subject: Chez Scheme
We would be interested in more info on Chez Scheme. Who can we contact ?
Since we are using an experimental connection from New Zealand, please
reply through either: wolfgang%cantuar@waterloo.csnet OR
...watmath!cantuar!wolfgang. Thanks. w.kreutzer Univ. of Canterbury, NZ
∂07-Aug-86 0136 @MC.LCS.MIT.EDU:JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU non-list arguments
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Date: Thu, 7 Aug 86 04:30:58 EDT
From: Jonathan A Rees <JAR%MX.LCS.MIT.EDU@MC.LCS.MIT.EDU>
Subject: non-list arguments
To: rhh@MC.LCS.MIT.EDU
cc: scheme@MC.LCS.MIT.EDU, t-discussion@MC.LCS.MIT.EDU
In-reply-to: Msg of Tue 1 Apr 86 15:26 EST from Robert Halstead <rhh at MIT-VAX.ARPA>
Message-ID: <[MX.LCS.MIT.EDU].939050.860807.JAR>
Date: Tue, 1 Apr 86 15:26 EST
From: Robert Halstead <rhh at MIT-VAX.ARPA>
To summarize, I think it should be permissible for
(eq? ((lambda x x) l) l)
to return true, but it should not be a requirement. Furthermore, it
should be permissible for an implementation to report an error if l in
the above expression is not a true list, but an implementation should
not be required to do so. Of course, it would still be true that
((lambda x x) 3 4 5)
would return a freshly consed list, just like (list 3 4 5). An
interesting question: do people expect (apply list l) to return a
top-level copy of l? -b.
Permitting sharing between the argument passed to apply and the
rest-argument leads to all kinds of obscure bugs - especially if sharing
isn't guaranteed. In fact I have written and used interpreters which
shared the list, and I regretted it every time. Efficiency shouldn't
guide the design on this issue. A compiler could easily detect the
situation you described (a rest-variable referenced only as the last
argument to APPLY) and generate code which doesn't cons.
Jonathan
∂07-Aug-86 0301 @MC.LCS.MIT.EDU:Pase@DOCKMASTER.ARPA Scheme for the Atari ST
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Date: Fri, 4 Apr 86 00:59 EST
From: Bill Pase <Pase@DOCKMASTER.ARPA>
Subject: Scheme for the Atari ST
To: scheme@MIT-MC.ARPA
Message-ID: <860404055925.041933@DOCKMASTER.ARPA>
Does anyone know if Scheme is available for the Atari ST? I know there
are versions for the IBMPC and the Macintosh. It wouIt would seem
especially with the later that an Atari version should be easy. Does
anyone have any plans to develop it? /bill
∂07-Aug-86 0730 @MC.LCS.MIT.EDU:jcm@ORNL-MSR.ARPA Re: Scheme for the Atari ST
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Date: Thu, 7 Aug 86 10:24:46 edt
From: jcm@ORNL-MSR.ARPA (James A. Mullens)
Message-Id: <8608071424.AA05596@ORNL-MSR.ARPA>
To: scheme@mit-mc
Subject: Re: Scheme for the Atari ST
from Bill Pase (Pase@DOCKMASTER.ARPA)
>Does anyone know if Scheme is available for the Atari ST?
I recently asked similar questions here, which lead me to some
history which may be helpful. I'll summarize what I've learned from
people on this list and the archives.
The archives for this group contain some references to "Scheme 312".
This is the ancestor of MacScheme. MacScheme is actually being
developed on the Stride (Sage) computer under the CP/M-68K operating
system, so the author has an decent version working in that
environment. (The author is not interested in distributing or
supporting that version, however).
I have heard that the Atari ST runs GEM on top of CP/M-68K (or a
minor mutation of CP/M). If this is true, it might be easy to port
to the Atari -- maybe easier than porting to the Mac. Perhaps the
author is not aware of this possibility and would be interested in
doing the port?
The author's name is Will Clinger, and he used to be at
willc%indiana.csnet@csnet-relay.arpa which is Indiana U on CSnet
from my ARPAnet BSD Unix machine. I'm not sure if he monitors this
list... The MacScheme distributor address:
Semantic Microsystems
4470 SW Hall Street, Suite 340
Beaverton OR 97005
(503) 643-4539
Dave Alcocer (alco@mit-vax) was working with CScheme. He says this
public domain version is portable. Dave said he was interested
having it on his Amiga, but it might need to be trimmed down from
approximately 2 megabytes by removing some trimmings.
Wouldn't it be amazing to see a group of Mac, Amiga, and ST owners
cooperating on a public domain Scheme!
The GNU project has started distributing CScheme. I'm not sure why
they have decided to do so.
Good Luck -
- jim mullens / oak ridge national lab
∂08-Aug-86 0819 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU
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Date: Fri, 8 Aug 86 11:16:47 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
To: wolfgang%cantuar%waterloo.csnet@CSNET-RELAY.ARPA
cc: scheme@MC.LCS.MIT.EDU
In-reply-to: Msg of Wed 6 Aug 86 19:30:29 nzt from Facilities Committee <facility%cantuar.waterloo.edu at CSNET-RELAY.ARPA>
Message-ID: <[AI.AI.MIT.EDU].80950.860808.JAR>
Date: Wed, 6 Aug 86 19:30:29 nzt
From: Facilities Committee <facility%cantuar.waterloo.edu at CSNET-RELAY.ARPA>
To: scheme < at CSNET-RELAY.ARPA, at watmath.waterloo.edu:scheme@MC.LCS.MIT.EDU>
Date: Thu, 31 Jul 86 10:44:24+1200
From: wolfgang@cantuar.Waterloo.edu (W. Kreutzer)
To: SCHEME@MIT-MC.csnet@watmath.Waterloo.edu
Subject: Chez Scheme
We would be interested in more info on Chez Scheme. Who can we contact ?
Since we are using an experimental connection from New Zealand, please
reply through either: wolfgang%cantuar@waterloo.csnet OR
...watmath!cantuar!wolfgang. Thanks. w.kreutzer Univ. of Canterbury, NZ
Implementation: Chez Scheme
Authored by: Kent Dybvig
Supported by: limited support by the author
Hardware: VAX
Operating Systems: 4.2 BSD UNIX (or ULTRIX)
Implementation: incrementally compiled to native code
Intended Use: education and research
Price: Per site: $400 for US colleges and universities,
and $1000 for companies who will use the
system for research and education only.
Chez Scheme was first released earlier this year and is now being used
at about 10 universities for classes and research. Chez Scheme supports
almost all of the required and optional features of the RRRS. The next
major release (in spring or summer 1986) will support 100% of the
required features of the standard.
In addition to the features of the RRRS, Chez Scheme provides error and
exception handling, engines, programmable cafes and waiters (fancy
read-eval-print loops), tracing and statistics- gathering facilities,
and fast-loading compiled files. Chez Scheme provides floating point
numbers, arbitrary-precision ratios, and arbitrary-precision integers,
but no imaginary numbers at this time.
Chez Scheme's biggest claim to fame is the speed and size of its
implementation. It outperforms Franz Lisp and DEC Common Lisp on most
programs, but the initial core image is less than 500K bytes, about half
of which is read-only and sharable.
For the license forms and ordering information, contact:
Kent Dybvig
Cadence Research Systems
620 Park Ridge Road
Bloomington, IN 47401
812/333-9269
You can also reach me during the day at 812/335-8653, or by electronic
mail to dyb.indiana@csnet-relay.
∂08-Aug-86 1230 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU [Masinter.pa: synonym streams..]
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Date: Fri, 8 Aug 86 11:19:12 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: [Masinter.pa: synonym streams..]
To: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].80953.860808.JAR>
How about a similar rule for Scheme? With the obvious extension to ports created by
with-input-file, etc.
- Jonathan.
Date: 5 Aug 86 11:09 PDT
From: Masinter.pa at Xerox.COM
To: common-lisp at su-ai.ARPA
Re: synonym streams..
In-reply-to: David Bein <pyramid!bein@hplabs.HP.COM>'s message of 5 Aug
86 09:05 PDT
Message-ID: <860805-111034-2460@Xerox>
I propose the following rule: "It is an error to attempt to close a
stream that wasn't created with open."
With this rule, it would follow that, since synonym, broadcast and
two-way streams are not created with open, it is an error to perform
"close" on them.
∂08-Aug-86 1712 @MC.LCS.MIT.EDU:Bartley%ti-csl.csnet@CSNET-RELAY.ARPA "Final" comments on RRRRS
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Date: Fri 8 Aug 86 15:20:50-CDT
From: David Bartley <Bartley%ti-csl.csnet@CSNET-RELAY.ARPA>
Subject: "Final" comments on RRRRS
To: RRRS-Authors%mit-mc@CSNET-RELAY.ARPA
Cc: Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
Message-Id: <12229239846.30.BARTLEY@CSC60>
Before I go on vacation, I'd like to submit a (very) few comments on the
current draft report for consideration for the SIGPLAN revision.
-- I'm very pleased with its appearance and happy that it was distributed
to all of the attendees at the LISP conference. Thanks again to Jonathon.
-- Kent Dybvig has asked that the colon (:) be removed from the set of
extended alphabetic characters (section 2.3). I agree completely. My
joint implementations of Scheme and Common LISP need a reasonable syntax
for Scheme procedures to refer to symbols in various Common LISP packages.
Using Common LISP's syntax seems best.
-- Reference [2] to our conference paper on PC Scheme may now be updated
to refer to pages 86-93 of the proceedings. The same goes for reference
[6] by Dybvig, Friedman, and Haynes. Reference [51] to the TI Scheme
manual should be changed from ``preliminary version 1.0, November 1985''
to ``Original issue: December 1985''.
-- I hope that Jonathon will be able to incorporate our proposed number
syntax.
Regards,
David Bartley
-------
∂11-Aug-86 0855 @MC.LCS.MIT.EDU,@MIT-MULTICS.ARPA:SRAUCH@UNBMVS1.BITNET Instructor's manual for S&ICP by Julie Sussman
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Date: 11 Aug 86 10:34:28 ADT
From: <SRAUCH@UNBMVS1>
To: scheme@mc.lcs.mit.edu
Subject: Instructor's manual for S&ICP by Julie Sussman
Message-ID: <ID45752.D860811.T103428.SRAUCH@UNBMVS1>
- Can anyone tell me whether the "Instructors Manual" for
Structure and Interpretation of Computer Programs by Abelson and
Sussman, written by Julie Sussman is available? If so, how can it be
obtained? McGraw-Hill Canada doesn't seem to have heard of it. Any help
with this would be greatly appreciated.
Steve R.
SRAUCH@UNBMVS1.BITNET
∂13-Aug-86 0238 NET-ORIGIN@MC.LCS.MIT.EDU Re: define
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Date: Wed, 16 Apr 86 13:06:41 PST
From: Will Clinger <willc%tekchips%tektronix.csnet@CSNET-RELAY.ARPA>
Message-Id: <8604162106.AA02612@tekchips>
To: SCHEME%MIT-MC%tektronix.csnet@CSNET-RELAY.ARPA
Subject: Re: define
Cc:
Roger Kirchner writes:
>Kent M Pitman said that there are other possible interpretations of
>(DEFINE (((...) ...) ...) ...)
>besides as an extended template for procedure definition.
>What would be the objections to making this interpretation standard?
Your interpretation is already standard, though not essential; see
page 18 of MIT AI Memo 848. Though other interpretations are possible,
they would be in conflict with the Revised Revised Report.
The extended syntax began in MIT Scheme and was picked up by MacScheme
and PC Scheme. T2 doesn't support it. I don't know about Chez Scheme
et cetera.
Peace, Will
∂14-Aug-86 1728 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Minutes from lunch 5 August 1986
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To: rrrs-authors@MC.LCS.MIT.EDU
Subject: Minutes from lunch 5 August 1986
In-Reply-To: Your message of Tue, 29 Jul 86 16:35:08 EDT.
<[AI.AI.MIT.EDU].77171.860729.JAR>
Date: 14 Aug 86 13:00:46 PDT (Thu)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
Minutes from lunch on Tuesday, 5 August 1986
Attendance was not taken.
Jonathan Rees was congratulated on getting a draft of the R↑3RS done in
time for the conference.
After lunch we drew up a list of language areas that need work. In a few
of these areas we have proposals on the table, while a few others are
difficult research areas:
ERRORS & INTERRUPTS. What are the errors? How are they signalled?
How are the handlers found, what do they do, how are they defined?
What about I/O devices?
OPAQUE TYPES. Three new procedures have been proposed for creating
and manipulating objects that answer false to all the standard type
predicates and cannot be taken apart by any of the standard deconstructors.
One procedure -- call it INJECT -- takes two objects and returns a new
opaque object consisting of the first object tagged by the second.
The second procedure -- call it IN? -- takes two objects and returns
true if the first object was created by calling INJECT with the second
object as the tag, and returns false otherwise. The third procedure --
call it PROJECT -- takes an opaque object and a tag object and returns
the object encapsulated by the opaque object provided the tags match.
Axiomatically:
(IN? (INJECT x y) y) ==> #t
(IN? (INJECT x y) z) ==> #f provided (NOT (EQV? y z))
(PROJECT (INJECT x y) y) ==> x
MACROS. Difficult research area. We're awaiting Eugene Kohlbecker's
thesis.
DYNAMIC-WIND. DYNAMIC-WIND seems like a good generalization of
UNWIND-PROTECT, but what about multiprocessing? Should an UNWIND/WIND
occur on every process switch? What about I/O? The formal semantics
of DYNAMIC-WIND is very operational, which I take to be a danger signal.
INPUT/OUTPUT. What should happen to the current ports on a process
switch? What should happen if the debugger gains control? What should
happen if a transcript is desired?
SYNCHRONIZATION. Ought to have some means of synchronization before we
have multiple processes.
MODULE SYSTEM. First class environments do most things right, but they
render inter-module constant folding (e.g. procedure integration)
impractical. I think we're finally agreed that the issue of first class
environments can usefully be separated from the question of incremental
definitions as used in S&ICP, and I don't think anyone is enthusiastic
about Common Lisp style packages as a mechanism for modularity.
SEMANTICS OF QUASIQUOTE, QUOTE. In question are things like (EQ? '(A) '(A))
and (SET-CAR! `(A B ,C) 3) and (SET-CAR! `(A B ,@C) 3). Does it matter to
the last two examples whether the compiler can determine that C is a
constant?
DECLARATIONS. It is important to be able to say things like "CAR is a
constant", "N is an exact nonnegative integer less than 2↑20", "This
procedure should be optimized for speed at the expense of space but
not safety". Which declarations signal an error if violated, and which
are merely hints for better performance? What is the syntax and scope
of a declaration?
SYNTAX CHECKER & CANONIZER. How about a program that converts programs
written in full Scheme into a canonical form that uses only the primitive
expressions, checking syntax as it does so? Tektronix has volunteered to
supply such a program.
VERIFICATION SUITE. How about a verification suite to locate bugs?
Someone volunteered to coordinate this, but I'm not sure I remember
who it was, so please re-volunteer.
BENCHMARK SUITE. This wasn't discussed at lunch, but I talked to
several people who would like to have a benchmark suite that generates
more meaningful and more easily interpreted numbers than do the Gabriel
benchmarks. For example, the Gabriel benchmarks test property lists
and fluid variables but don't do anything with lexical closures.
MULTIPLE RETURN VALUES. Two new procedures have been proposed for
multiple return values. One procedure -- call it RETURN -- takes
arbitrarily many values and returns them. The other procedure --
call it RECEIVE-VALUES -- takes a thunk and a procedure, and calls
the procedure on the (possibly multiple) values returned by the
thunk. The semantics that appears in R↑3RS was designed to work
with multiple return values, but we might want to change the help
function "single" so that extra return values (e.g. in the test
position of a conditional) are ignored as in Common Lisp. (With
the current version of "single", extra return values would be an
error.) Since RETURN doesn't do anything remotely like what RETURN
does in Common Lisp (and is identical to CL's VALUES function),
we might want to discuss the name. We might also want to discuss
the argument order for RECEIVE-VALUES.
OPTIONALS. Should there be a special syntax for optional arguments
so we don't have to use a rest argument and destructure it ourselves?
What should the syntax be?
∂14-Aug-86 1855 @MC.LCS.MIT.EDU:ANDY@Sushi.Stanford.EDU Re: Minutes from lunch 5 August 1986
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Date: Thu 14 Aug 86 18:30:00-PDT
From: Andy Freeman <ANDY@Sushi.Stanford.EDU>
Subject: Re: Minutes from lunch 5 August 1986
To: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
cc: rrrs-authors@MC.LCS.MIT.EDU
In-Reply-To: <8608142000.AA24878@tekchips.TEK>
Message-ID: <12230868993.15.ANDY@Sushi.Stanford.EDU>
I'd be happier if the Scheme community said nothing about
multitasking, multiprocessing, or anything related to parallelism.
This isn't intended to discourage informal communication, but any hint
of agreement/standardization is premature.
Why is this coming up now anyway? We don't understand macros, errors,
interrupts, declarations, etc.
I'd rather have (hash) tables than project/inject/in?.
-andy
-------
∂14-Aug-86 2053 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA substring indexes
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To: kend%tekla.tek.csnet@CSNET-RELAY.ARPA
Cc: rrrs-authors@MC.LCS.MIT.EDU
Subject: substring indexes
In-Reply-To: Your message of 13 Aug 86 08:37:36 PDT (Wed).
<8608131537.AA25142@tekla.TEK>
Date: 14 Aug 86 13:09:33 PDT (Thu)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
The following comes from Ken Dickey (kend@tekla). I favor changing
the description of substring-fill! to say START *to* END. Peace, Will.
----------------------------------------------------------------
Will,
I have not yet read the full report, but R-cubed is a significant
improvement over R-squared. I did find section 6.7 on strings,
however, to be somewhat confusing. Some functions (eg substring) use
START *to* END, while others (eg substring-fill!) use START *through*
END.
I think it would be better to either maintain
0 <= START <= END < (string-length <string>)
XOR use 1 based indexing.
In both cases, I favor using start through end (both inclusive). The
latter is probably more in keeping with the spirit of Scheme in that
one based indexing seems more natural to naive programmers**.
Pax,
-Ken
-------------
** (based on my experience teaching Pascal and C).
∂14-Aug-86 2233 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA r-cubed syntax (nits)
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To: JAR@AI.AI.MIT.EDU
Cc: rrrs-authors@MC.LCS.MIT.EDU
Subject: r-cubed syntax (nits)
In-Reply-To: Your message of Tue, 29 Jul 86 16:35:08 EDT.
<[AI.AI.MIT.EDU].77171.860729.JAR>
Date: 14 Aug 86 13:58:14 PDT (Thu)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
The following comes from Ken Dickey (kend%tekla@tek.csnet; my previous
note said kend@tekla, but I don't think that works unless you're at
Tektronix.).
----------------------------------------------------------------
Will,
parsimony: 7.1.1: <suffix>:
<digit> <digit>*
can be written <digit>+
ambiguity?: 7.1.3: <case clause> and <cond clause> both allow
(else <sequence>)
to be any clause, rather than the last clause. Is this intentional?
Again, let me say that this is the best language spec that I have read
in some time (I still have 7.2 to slog through).
-Ken
∂15-Aug-86 0902 @MC.LCS.MIT.EDU:dyb%iuvax.indiana.edu@CSNET-RELAY.ARPA Re: Minutes from lunch 5 August 1986
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Date: Fri, 15 Aug 86 00:51:46 est
From: "R. Kent Dybvig" <dyb%iuvax.indiana.edu@CSNET-RELAY.ARPA>
To: rrrs-authors%mit-mc.CSNET@CSNET-RELAY.ARPA
Subject: Re: Minutes from lunch 5 August 1986
It was I who volunteered to coordinate the verification suite.
Kent
∂15-Aug-86 1106 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU r-cubed syntax (nits)
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Date: Fri, 15 Aug 86 13:47:03 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: r-cubed syntax (nits)
To: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
cc: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of 14 Aug 86 13:58:14 PDT (Thu) from willc%tekchips.tek.csnet at CSNET-RELAY.ARPA
Message-ID: <[AI.AI.MIT.EDU].84074.860815.JAR>
Date: 14 Aug 86 13:58:14 PDT (Thu)
From: willc%tekchips.tek.csnet at CSNET-RELAY.ARPA
parsimony: 7.1.1: <suffix>:
<digit> <digit>*
can be written <digit>+
OK, will fix.
ambiguity?: 7.1.3: <case clause> and <cond clause> both allow
(else <sequence>)
to be any clause, rather than the last clause. Is this intentional?
I had it this way for a while, and decided that it was unnecessary
clutter in the syntax. You need to give two rules instead of one for
the syntax of cond (and case), and it looks really bad. But the fact
that someone noticed & cared is probably enough to indicate that I
should change it back to the more verbose, pedantic form.
∂15-Aug-86 1112 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU scheme report tar file
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Date: Fri, 15 Aug 86 13:57:51 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: scheme report tar file
To: goodhart@NOSC-COD.ARPA
cc: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Wed 6 Aug 86 10:26:55 PDT from Curtis L. Goodhart <goodhart%cod at nosc.ARPA>
Message-ID: <[AI.AI.MIT.EDU].84083.860815.JAR>
OK, there's now a tar file for the draft of the scheme report on host
MIT-PREP in the file "/u/jar/r3rs.tar". Use user scheme password scheme
if user & password are required. The tar file is about .25 Mbytes.
Sorry this took so long.
Jonathan
∂15-Aug-86 1223 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU "Final" comments on RRRRS
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Date: Fri, 15 Aug 86 15:22:44 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: "Final" comments on RRRRS
To: Bartley%ti-csl.csnet@CSNET-RELAY.ARPA
cc: RRRS-Authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Fri 8 Aug 86 15:20:50-CDT from David Bartley <Bartley%ti-csl.csnet at CSNET-RELAY.ARPA>
Message-ID: <[AI.AI.MIT.EDU].84135.860815.JAR>
Date: Fri 8 Aug 86 15:20:50-CDT
From: David Bartley <Bartley%ti-csl.csnet at CSNET-RELAY.ARPA>
-- Kent Dybvig has asked that the colon (:) be removed from the set of
extended alphabetic characters (section 2.3). I agree completely. My
joint implementations of Scheme and Common LISP need a reasonable syntax
for Scheme procedures to refer to symbols in various Common LISP packages.
Using Common LISP's syntax seems best.
I have no strong objection to this. It's conceivable that it could be
construed by the uninitiated as an endorsement of read-time packaging,
but I think we should be able to guard against that.
I would like to hear from people who object to the this (Hanson?)
before making the change. If the screams aren't too loud I'll do it.
-- I hope that Jonathan will be able to incorporate our proposed number
syntax.
Sorry, I just won't have time to work on it, and I don't think there's
time for proper review. If you could prepare the changes in fine detail
(maybe edit the TeX sources yourself), this might be feasible, but a
last-minute change of this magnitude is bound to have problems with it.
Probably it would be best to just include a statement to the effect that
this change is being considered for a future revision of the report.
Jonathan
∂15-Aug-86 2150 @MC.LCS.MIT.EDU:CPH@AI.AI.MIT.EDU "Final" comments on RRRRS
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Date: Sat, 16 Aug 86 00:50:15 EDT
From: Chris Hanson <CPH@AI.AI.MIT.EDU>
Subject: "Final" comments on RRRRS
To: JAR@AI.AI.MIT.EDU
cc: RRRS-Authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Fri 15 Aug 86 15:22:44 EDT from Jonathan A Rees <JAR at AI.AI.MIT.EDU>
Message-ID: <[AI.AI.MIT.EDU].84332.860816.CPH>
Date: Fri, 15 Aug 86 15:22:44 EDT
From: Jonathan A Rees <JAR at AI.AI.MIT.EDU>
To: Bartley%ti-csl.csnet at CSNET-RELAY.ARPA
Date: Fri 8 Aug 86 15:20:50-CDT
From: David Bartley <Bartley%ti-csl.csnet at CSNET-RELAY.ARPA>
-- Kent Dybvig has asked that the colon (:) be removed from
the set of extended alphabetic characters (section 2.3). I
agree completely. My joint implementations of Scheme and
Common LISP need a reasonable syntax for Scheme procedures to
refer to symbols in various Common LISP packages. Using
Common LISP's syntax seems best.
I have no strong objection to this. It's conceivable that it could be
construed by the uninitiated as an endorsement of read-time packaging,
but I think we should be able to guard against that.
I would like to hear from people who object to the this (Hanson?)
before making the change. If the screams aren't too loud I'll do it.
I guess that I should respond to this. I really, truly abhor the
read-time package system and would strenuously object to any such
thing being introduced into Scheme. I have gone out of my way (a
little) to use colons in my code just to parody the package system
and, unfortunately, that would make my code non-portable given this
decision.
Understand, I have no really serious objections to this suggestion,
except that if anyone tries to define what `:' means when it appears
in an identifier, I promise to raise heck. But I don't mind agreeing
to disagree about it.
And, of course, anyone who implements this change will not be able to
port my code without significant rewriting. Sigh. I guess that would
be your loss, not mine.
(Seriously, though, what would the symbol
`rtl:interpreter-call:lookup' mean in a system with such a syntax?)
∂18-Aug-86 0051 @MC.LCS.MIT.EDU:ram@YALE.ARPA Re: The generality of define
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From: Ashwin Ram <ram@YALE.ARPA>
Message-Id: <8604240246.AA12180@Yale-Bulldog.YALE.ARPA>
Subject: Re: The generality of define
To: andy@aids-unix.ARPA (Andy Cromarty)
Cc: SCHEME@MC.LCS.MIT.EDU
In-Reply-To: andy@aids-unix.ARPA (Andy Cromarty), Wed, 23 Apr 86 19:09:53 EST
Date: 21 Apr 1986 09:43-PST
From: andy@aids-unix (Andy Cromarty)
Subject: Re: The generality of define
Actually, a properly implemented
(define (square x) (* x x))
is not equivalent to
(define square (lambda (x) (* x x)))
at all, but rather to
(define square (rec square (lambda (x) (* x x))))
(define (fact1 n)
(if (<? n 2)
1
(* n (fact1 (-1+ n)))))
(define fact2
(lambda (n)
(if (<? n 2)
1
(* n (fact2 (-1+ n))))))
asc
-------
In T there is *no* difference between these two forms (except that you
get a named-lambda in the first case rather than a lambda).
> (pp copy1)
(LAMBDA (N) (IF (<? N 2) 1 (* N (FACT1 (-1+ N))))) <<<<| Both closed
| in the same
> (pp copy2) | environment.
(LAMBDA (N) (IF (<? N 2) 1 (* N (FACT2 (-1+ N))))) <<<<|
> (copy1 5)
20
> (copy2 5)
20
This makes sense to me since (DEFINE (FOO ...) ...) is specified to
be equivalent to (DEFINE FOO (LAMBDA (...) ...)). In both cases, FOO is
defined to be a closure whose environment is the environment of definition,
i.e., the REPL-ENV.
To get the definition analogous to your REC case, you need to use LABELS
explicitly:
> (define fact3
(labels (((fact3 n) (if (< n 2) 1 (* n (fact3 (-1+ n))))))
fact3))
> (define copy3 fact3)
> (define fact3 (lambda (x) x))
> (copy3 5)
120
It might make more sense to make this the default expansion since you
would usually expect the recursive call to refer to the definition-time
procedure (as opposed to its "name"), though now the variables FACT3 and
N have different reference semantics within the same form. In the case of
two or more mutually recursive functions, you still have to rely on the
run-time values of the cells that the variables in the closure refer to
in the environment that the closure was defined in. It's debatable,
therefore, whether special reference semantics for the name of the lambda
form is the "proper implementation", though it does seem more natural
albeit hairier.
-- Ashwin.
-------
∂18-Aug-86 1650 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA define syntax (an apology)
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To: scheme@MC.LCS.MIT.EDU
Cc: willc%tekchips.tek.com@CSNET-RELAY.ARPA
Subject: define syntax (an apology)
In-Reply-To: Your message of Fri, 15 Aug 86 13:47:03 EDT.
<[AI.AI.MIT.EDU].84074.860815.JAR>
Date: 18 Aug 86 10:45:30 PDT (Mon)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
A message I sent several months ago recently made it to this mailing list.
By now, my message is incorrect. I wish to apologize for the confusion I
have caused.
There is an important difference between the 1985 Scheme standard (MIT AI
Memo 848) and the draft of the new 1986 Scheme standard (distributed at
the ACM Conference on Lisp and Functional Programming and expected to
appear in November SIGPLAN Notices). In the 1985 standard
(define (foo ...) ...)
was equivalent to
(define foo (rec foo (lambda (...) ...))).
In the 1986 standard (define (foo ...) ...) is equivalent to
(define foo (lambda (...) ...)).
As I understand it, the motivation for this change is that in the 1985
semantics, mutual recursion goes through the obvious binding of foo,
but self-recursion goes through the invisible (and therefore mysterious)
binding of foo created by the implicit rec. It's hard to explain why
self-recursion should behave differently from mutual recursion, so the
1986 semantics gets rid of the implicit rec and the mystery.
This change was inadvertently omitted from the list of changes that
appears in the draft distributed at the Lisp conference, so you have
to read the draft very carefully to spot it. By the way, the
(define ((foo ...) ...) ...) syntax was also dropped from the draft
as a simplifying measure.
Peace, Will
∂20-Aug-86 2002 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA numbers
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To: rrrs-authors@MC.LCS.MIT.EDU
Cc: willc%tekchips.tek.com@CSNET-RELAY.ARPA,
adams%tekchips.tek.com@CSNET-RELAY.ARPA
Subject: numbers
In-Reply-To: Your message of Wed 16 Jul 86 10:53:32-CDT.
<12223161873.35.BARTLEY@CSC60>
Date: 20 Aug 86 17:13:20 PDT (Wed)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
Abstract: Scheme numbers are still inadequately specified in several
respects. I propose several improvements. Some are minor enough to
deserve incorporation in the SIGPLAN Notices publication of the Revised↑3
Report, but the others probably deserve more debate.
Some problems that I perceive with Scheme numbers are:
1. The quotient procedure is not adequately specified.
2. The floor etc procedures are not adequately specified.
3. The syntax for numbers has a redundancy.
4. The integer? procedure may not be adequately specified.
5. Valid indexes may not be adequately specified.
6. The read and string->number procedures are not adequately specified.
(David Bartley has also suggested that the syntax should be made more
compatible with Common Lisp and has proposed that the report be clearer
on which parts of the number syntax are essential and which are not
essential.)
1. Norman Adams pointed out to me that it is unclear from the description
of quotient in 6.5.4 whether (quotient -13 4) should be -3 or -4; likewise
(quotient 13 -4). I propose that the sentence beginning "For positive
integers n1 and n2" be followed by the sentence
For all integers n1 and n2 with n2 not equal to 0,
(= n1 (+ (* n2 (quotient n1 n2)) (remainder n1 n2))) ==> #t
2. In the description of floor, ceiling, truncate, round, and rationalize,
the sentence "Their results are not exact---in fact, their results are
clearly inexact, though they can be made exact with an explicit exactness
coercion" is incorrect. I propose that the sentence be replaced by "Their
results are exact if and only if their arguments are exact."
3. The third production for <ureal R> is redundant.
4. In MacScheme and a few other implementations, (integer? 4.0) evaluates
to #f. Even assuming that 4.0 is inexact, this seems wrong. I would like
to see an example in the report to show that it's wrong.
5. I believe the index or size arguments to list-tail, list-ref,
make-string, string-ref, string-set!, substring-fill!, make-vector,
vector-ref, and vector-set! should be required to be exact integers
instead of just integers.
6. It isn't clear from the report whether 3.0 reads as an exact or inexact
number. Indeed the same can be said of 3, or 3/1, or 3###-4###i. I propose
that this sort of thing be specified more formally, as in the following
example---which does not match up very well with the syntax and is not my
favorite proposal anyway.
exactness [ <real> + <ureal> i ] = exactness [ <real> - <ureal> i ]
= minexact (exactness [ <real> ], exactness [ ureal ])
exactness [ <real←1> @ <real←2> ]
= minexact (exactness [ <real←1> ], exactness [ <real←2> ]
exactness [ <sign> <ureal> ] = exactness [ <ureal> ]
exactness [ <prefix> <x> <suffix> ]
= if explicit [ <prefix> ]
then prexact [ <prefix> ]
else if empty [ <suffix> ]
then exactness [ <x> ]
else #f ; this is what I don't like
exactness [ <uinteger> <suffix> ]
= if empty [ <suffix> ] then exactness [ <uinteger> ] else #f
exactness [ <digit>+ #+ ] = #f
exactness [ <digit>+ ] = #t
exactness [ <uinteger←1> / <uinteger←2> ]
= minexact (exactness [ <uinteger←1> ], exactness [ <uinteger←2> ])
exactness [ <digit>+ #+ ] = #f
exactness [ <digit>+ ] = #t
exactness [ <digit>* . <digit>+ #* ] = #f
exactness [ <digit>* . #+ ] = #f
exactness [ <digit>+ . ] = #t
exactness [ <digit>+ #+ . ] = #f
minexact (b1, b2) = if b1 then b2 else #f
explicit [ ... #i ... ] = explicit [ ... #e ... ] = #t
explicit [ ... <empty exactness> ... ] = #f
prexact [ ... <exactness> ... ] = prexact [ <exactness> ]
prexact [ #i ] = #f
prexact [ #e ] = #t
Peace, Will
∂22-Aug-86 0555 @MC.LCS.MIT.EDU:dyb%iuvax.indiana.edu@CSNET-RELAY.ARPA a few more comments
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Date: Fri, 22 Aug 86 03:03:54 est
From: "R. Kent Dybvig" <dyb%iuvax.indiana.edu@CSNET-RELAY.ARPA>
To: rrrs-authors%mit-mc.CSNET@CSNET-RELAY.ARPA
Subject: a few more comments
It may be too late to bother with any of this, but here are a few
comments on the R3RS copy handed out at the conference.
Functionality
-------------
char-ready? looks too much like char-lower-case?, char-alphabetic?,
etc., and not enough like read-char. I think read-char-ready? would
be much more appropriate. Besides, some implementation or future
RnRS may want to have a write-char-ready?. Is there any reason not
to change the name?
In the number formats, the syntax (exactness) is used within two of
the examples of 6.5.6, but this form is not explicitly allowed in
6.5.7. My feeling is that the modifier s or e should be required,
as implied in 6.5.7. The formats are pretty complicated as is.
What happens on string<?, string>?, string<=?, string>=?, string-ci<?,
string-ci>?, string-ci<=?, string-ci>=? when one string is longer
than the other? I would add "If two strings differ in length but
are the same up to the length of the shorter string, the shorter string
is considered to be lexographically less than the longer string".
The procedure substring-fill! is the only procedure left that sticks
out to me as unnecessary and rarely useful. Perhaps someone can
explain to me why it should be in the standard.
Why is there not a vector-null? function..., or why not delete null?
and string-null? to be consistent?
Presentation
------------
1.3.1 strike the word "will"
2.1 it is not clear what "extended alphabetic characters" are here;
I think that the list should be moved here from 2.3, which is, after
all, titled "other" notations. At the least, a forward pointer is
needed.
2.1 last sentence, replace "between" with "among"
2.3 mention that ) is used to close a vector constant
6.9 optional if syntax should not be used in example
True Nitpick
------------
7.3 in first case description...
(let ((key <key> )
↑ extra space
Kent
∂22-Aug-86 1208 @MC.LCS.MIT.EDU,@SEBASTIAN.THINK.COM:gls@AQUINAS.THINK.COM 1986 Lisp conference bibliography
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From: Guy Steele <gls@Think.COM>
Subject: 1986 Lisp conference bibliography
To: common-lisp@SU-AI.ARPA, rrrs-authors@MC.LCS.MIT.EDU
Cc: gls@AQUINAS
Message-Id: <860822140628.4.GLS@SEBASTIAN.THINK.COM>
With the help of Bill Scherlis, I have massaged the table of contents
(with some corrections) for the 1986 ACM Conference on Lisp and
Functional Programming into the form of a bibliography database suitable
for use with LaTeX/BibTeX and (almost) SCRIBE. The database has been
tested with BibTeX, and uses TeX conventions for forcing capitalization
and for accenting characters (there are three accents acute, one umlaut,
and one "i" with a circumflex over it). The database should require
only slight modification to make it suitable for use with SCRIBE.
I am mailing out the database in the interest of making it easier for
everyone to refer to all these great papers from the conference. The
database follows at the end of this message, followed by the BibTeX
transcription of it for a bibliography format very similar to that
required by CACM. (I considered just mailing out a pointer to an
FTP-able file, but I find that in practice this method is rather clumsy
and people don't use it.)
--Guy
----------------------------------------------------------------
@InProceedings(LAWS-IN-MIRANDA
,Key = "Thompson"
,Author = "Simon Thompson"
,Title = "Laws in {M}iranda"
,Pages = "1-12"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(MINI-ML
,Key = "Clement"
,Author = "Dominique Cl\'ement and {Jo\"elle} Despeyroux and Thierry Despeyroux and Gilles Kahn"
,Title = "A Simple Applicative Language: {M}ini-{ML}"
,Pages = "13-27"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(INTEGRATING-FUNCTIONAL-AND-IMPERATIVE-PROGRAMMING
,Key = "Gifford"
,Author = "David K. Gifford and John M. Lucassen"
,Title = "Integrating Functional and Imperative Programming"
,Pages = "28-38"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(EXPERIENCE-WITH-AN-UNCOMMON-LISP
,Key = "Alberga"
,Author = "Cyril N. Alberga and Chris Bosman-Clark and Martin Mikelsons and Mary S. Van Deusen and Julian Padget"
,Title = "Experience with an Uncommon {L}isp"
,Pages = "39-53"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(DESIDERATA-FOR-THE-STANDARDISATION-OF-LISP
,Key = "Padget"
,Author = "Julian Padget and others"
,Title = "Desiderata for the Standardisation of {L}isp"
,Pages = "54-66"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(OPTIMIZING-DYNAMICALLY-RETARGETABLE-COMPILER-FOR-COMMON-LISP
,Key = "Brooks"
,Author = "Rodney A. Brooks and David B. Posner and James L. McDonald and Jon L. White and Eric Benson and Richard P. Gabriel"
,Title = "Design of an Optimizing, Dynamically Retargetable Compiler for {C}ommon {L}isp"
,Pages = "67-85"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(IMPLEMENTATION-OF-PC-SCHEME
,Key = "Bartley"
,Author = "David H. Bartley and John C. Jensen"
,Title = "The Implementation of {PC} {S}cheme"
,Pages = "86-93"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(CODE-GENERATION-TECHNIQUES-FOR-FUNCTIONAL-LANGUAGES
,Key = "Fairbairn"
,Author = "Jon Fairbairn and Stuart C. Wray"
,Title = "Code Generation Techniques for Functional Languages"
,Pages = "94-104"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(ARCHITECTURE-FOR-MOSTLY-FUNCTIONAL-LANGUAGES
,Key = "Knight"
,Author = "Tom Knight"
,Title = "An Architecture for Mostly Functional Languages"
,Pages = "105-112"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(EFFICIENT-MULTIPROCESSOR-COMBINATOR-REDUCTION
,Key = "Lemaitre"
,Author = "M. Lema\↑\itre and M. Castan and M.-H. Durand and G. Durrieu and B. Lecussan"
,Title = "Mechanisms for Efficient Multiprocessor Combinator Reduction"
,Pages = "113-121"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(CURRY-CHIP
,Key = "Ramsdell"
,Author = "John D. Ramsdell"
,Title = "The {CURRY} Chip"
,Pages = "122-131"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(VARIATIONS-ON-STRICTNESS-ANALYSIS
,Key = "Bloss"
,Author = "Adrienne Bloss and Paul Hudak"
,Title = "Variations on Strictness Analysis"
,Pages = "132-142"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(EXPANSION-PASSING-STYLE
,Key = "Dybvig"
,Author = "R. Kent Dybvig and Daniel P. Friedman and Christopher T. Haynes"
,Title = "Expansion-Passing Style: Beyond Conventional Macros"
,Pages = "143-150"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(HYGIENIC-MACRO-EXPANSION
,Key = "Kohlbecker"
,Author = "Eugene Kohlbecker and Daniel P. Friedman and Matthias Felleisen and Bruce Duba"
,Title = "Hygienic Macro Expansion"
,Pages = "151-161"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(EXACT-REAL-ARITHMETIC
,Key = "Boehm"
,Author = "Hans-J. Boehm and Robert Cartwright and Mark Riggle and Michael J. O'Donnell"
,Title = "Exact Real Arithmetic: A Case Study in Higher Order Programming"
,Pages = "162-173"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(RECONFIGURABLE-RETARGETABLE-BIGNUMS
,Key = "White"
,Author = "Jon L. White"
,Title = "Reconfigurable, Retargetable Bignums: A Case Study in Efficient, Portable {L}isp System Building"
,Pages = "174-191"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(LISP-ON-A-REDUCED-INSTRUCTION-SET-PROCESSOR
,Key = "Steenkiste"
,Author = "Peter Steenkiste and John Hennessy"
,Title = "{L}isp on a Reduced-Instruction-Set-Processor"
,Pages = "192-201"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(PARTITIONING-PARALLEL-PROGRAMS-FOR-MACRO-DATAFLOW
,Key = "Sarkar"
,Author = "Vivek Sarkar and John Hennessy"
,Title = "Partitioning Parallel Programs for Macro-Dataflow"
,Pages = "202-211"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(NORMA-GRAPH-REDUCTION-PROCESSOR
,Key = "Scheevel"
,Author = "Mark Scheevel"
,Title = "{NORMA}: A Graph Reduction Processor"
,Pages = "212-219"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(FOUR-STROKE-REDUCTION-ENGINE
,Key = "Clack"
,Author = "Chris Clack and Simon L. Peyton Jones"
,Title = "The Four-Stroke Reduction Engine"
,Pages = "220-232"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(USE-OF-LISP-IN-IMPLEMENTING-DENOTATIONAL-SEMANTICS
,Key = "Lee"
,Author = "Peter Lee and Uwe Pleban"
,Title = "On the Use of {L}isp in Implementing Denotational Semantics"
,Pages = "233-248"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(SEMANTICS-DIRECTED-COMPILING-FOR-FUNCTIONAL-LANGUAGES
,Key = "Nielson"
,Author = "Hanne R. Nielson and Flemming Nielson"
,Title = "Semantics Directed Compiling for Functional Languages"
,Pages = "249-257"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(CONNECTION-GRAPHS
,Key = "Bawden"
,Author = "Alan Bawden"
,Title = "Connection Graphs"
,Pages = "258-265"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(IMPLEMENTING-FUNCTIONAL-LANGUAGES-IN-THE-CATEGORICAL-ABSTRACT-MACHINE
,Key = "Mauny"
,Author = "Michel Mauny and Asc\'ander Su\'arez"
,Title = "Implementing Functional Languages in the Categorical Abstract Machine"
,Pages = "266-278"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(CONNECTION-MACHINE-LISP
,Key = "Steele"
,Author = "Steele, Guy L., Jr. and W. Daniel Hillis"
,Title = "Connection Machine LISP: Fine-Grained Parallel Symbolic Processing"
,Pages = "279-297"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(MYSTERY-OF-THE-TOWER-REVEALED
,Key = "Wand"
,Author = "Mitchell Wand and Daniel P. Friedman"
,Title = "The Mystery of the Tower Revealed: A Non-Reflective Description of the Reflective Tower"
,Pages = "298-307"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(TYPE-INFERENCE-APPROACH-TO-POLYMORPHIC-EXPRESSIONS
,Key = "Mitchell"
,Author = "John C. Mitchell"
,Title = "A Type-Inference Approach to Reduction Properties and Semantics of Polymorphic Expressions (summary)"
,Pages = "308-319"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(EQUATIONS-SETS-AND-REDUCTION-SEMANTICS
,Key = "Jayaraman"
,Author = "Bharat Jayaraman and Frank S. K. Silbermann"
,Title = "Equations, Sets, and Reduction Semantics for Functional and Logic Programming"
,Pages = "320-331"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(SEMANTIC-THEORY-FOR-EQUATIONAL-PROGRAMMING-LANGUAGES
,Key = "Thatte"
,Author = "Satish R. Thatte"
,Title = "Towards a Semantic Theory for Equational Programming Languages"
,Pages = "332-342"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(PROTOCOL-FOR-DISTRIBUTED-REFERENCE-COUNTING
,Key = "Lermen"
,Author = "Claus-Werner Lermen and Dieter Maurer"
,Title = "A Protocol for Distributed Reference Counting"
,Pages = "343-350"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(SEMANTIC-MODEL-OF-REFERENCE-COUNTING-AND-ITS-ABSTRACTION
,Key = "Hudak"
,Author = "Paul Hudak"
,Title = "A Semantic Model of Reference Counting and its Abstraction (detailed summary)"
,Pages = "351-363"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
@InProceedings(DISTRIBUTED-COPYING-GARBAGE-COLLECTION
,Key = "Rudalics"
,Author = "Martin Rudalics"
,Title = "Distributed Copying Garbage Collection"
,Pages = "364-372"
,Booktitle = "Proc.~1986 ACM Conference on Lisp and Functional Programming"
,Organization = "ACM SIGPLAN/SIGACT/SIGART"
,Year = "1986"
,Month = Aug
,Address = "Cambridge, Massachusetts")
----------------------------------------------------------------
\bibitem{EXPERIENCE-WITH-AN-UNCOMMON-LISP}
Alberga, Cyril N., Bosman-Clark, Chris, Mikelsons, Martin, Deusen, Mary S. Van, and Padget, Julian.
Experience with an uncommon {L}isp.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 39--53.
\bibitem{IMPLEMENTATION-OF-PC-SCHEME}
Bartley, David H., and Jensen, John C.
The implementation of {PC} {S}cheme.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 86--93.
\bibitem{CONNECTION-GRAPHS}
Bawden, Alan.
Connection graphs.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 258--265.
\bibitem{VARIATIONS-ON-STRICTNESS-ANALYSIS}
Bloss, Adrienne, and Hudak, Paul.
Variations on strictness analysis.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 132--142.
\bibitem{EXACT-REAL-ARITHMETIC}
Boehm, Hans-J., Cartwright, Robert, Riggle, Mark, and O'Donnell, Michael J.
Exact real arithmetic: a case study in higher order programming.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 162--173.
\bibitem{OPTIMIZING-DYNAMICALLY-RETARGETABLE-COMPILER-FOR-COMMON-LISP}
Brooks, Rodney A., Posner, David B., McDonald, James L., White, Jon L., Benson, Eric, and Gabriel, Richard P.
Design of an optimizing, dynamically retargetable compiler for {C}ommon {L}isp.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 67--85.
\bibitem{FOUR-STROKE-REDUCTION-ENGINE}
Clack, Chris, and Jones, Simon L. Peyton.
The four-stroke reduction engine.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 220--232.
\bibitem{MINI-ML}
Cl\'ement, Dominique, Despeyroux, {Jo\"elle}, Despeyroux, Thierry, and Kahn, Gilles.
A simple applicative language: {M}ini-{ML}.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 13--27.
\bibitem{EXPANSION-PASSING-STYLE}
Dybvig, R. Kent, Friedman, Daniel P., and Haynes, Christopher T.
Expansion-passing style: beyond conventional macros.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 143--150.
\bibitem{CODE-GENERATION-TECHNIQUES-FOR-FUNCTIONAL-LANGUAGES}
Fairbairn, Jon, and Wray, Stuart C.
Code generation techniques for functional languages.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 94--104.
\bibitem{INTEGRATING-FUNCTIONAL-AND-IMPERATIVE-PROGRAMMING}
Gifford, David K., and Lucassen, John M.
Integrating functional and imperative programming.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 28--38.
\bibitem{SEMANTIC-MODEL-OF-REFERENCE-COUNTING-AND-ITS-ABSTRACTION}
Hudak, Paul.
A semantic model of reference counting and its abstraction (detailed summary).
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 351--363.
\bibitem{EQUATIONS-SETS-AND-REDUCTION-SEMANTICS}
Jayaraman, Bharat, and Silbermann, Frank S. K.
Equations, sets, and reduction semantics for functional and logic programming.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 320--331.
\bibitem{ARCHITECTURE-FOR-MOSTLY-FUNCTIONAL-LANGUAGES}
Knight, Tom.
An architecture for mostly functional languages.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 105--112.
\bibitem{HYGIENIC-MACRO-EXPANSION}
Kohlbecker, Eugene, Friedman, Daniel P., Felleisen, Matthias, and Duba, Bruce.
Hygienic macro expansion.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 151--161.
\bibitem{USE-OF-LISP-IN-IMPLEMENTING-DENOTATIONAL-SEMANTICS}
Lee, Peter, and Pleban, Uwe.
On the use of {L}isp in implementing denotational semantics.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 233--248.
\bibitem{EFFICIENT-MULTIPROCESSOR-COMBINATOR-REDUCTION}
Lema\↑\itre, M., Castan, M., Durand, M.-H., Durrieu, G., and Lecussan, B.
Mechanisms for efficient multiprocessor combinator reduction.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 113--121.
\bibitem{PROTOCOL-FOR-DISTRIBUTED-REFERENCE-COUNTING}
Lermen, Claus-Werner, and Maurer, Dieter.
A protocol for distributed reference counting.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 343--350.
\bibitem{IMPLEMENTING-FUNCTIONAL-LANGUAGES-IN-THE-CATEGORICAL-ABSTRACT-MACHINE}
Mauny, Michel, and Su\'arez, Asc\'ander.
Implementing functional languages in the categorical abstract machine.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 266--278.
\bibitem{TYPE-INFERENCE-APPROACH-TO-POLYMORPHIC-EXPRESSIONS}
Mitchell, John C.
A type-inference approach to reduction properties and semantics of polymorphic expressions (summary).
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 308--319.
\bibitem{SEMANTICS-DIRECTED-COMPILING-FOR-FUNCTIONAL-LANGUAGES}
Nielson, Hanne R., and Nielson, Flemming.
Semantics directed compiling for functional languages.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 249--257.
\bibitem{DESIDERATA-FOR-THE-STANDARDISATION-OF-LISP}
Padget, Julian, et al.
Desiderata for the standardisation of {L}isp.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 54--66.
\bibitem{CURRY-CHIP}
Ramsdell, John D.
The {CURRY} chip.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 122--131.
\bibitem{DISTRIBUTED-COPYING-GARBAGE-COLLECTION}
Rudalics, Martin.
Distributed copying garbage collection.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 364--372.
\bibitem{PARTITIONING-PARALLEL-PROGRAMS-FOR-MACRO-DATAFLOW}
Sarkar, Vivek, and Hennessy, John.
Partitioning parallel programs for macro-dataflow.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 202--211.
\bibitem{NORMA-GRAPH-REDUCTION-PROCESSOR}
Scheevel, Mark.
{NORMA}: a graph reduction processor.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 212--219.
\bibitem{CONNECTION-MACHINE-LISP}
Steele, Jr., Guy L., and Hillis, W. Daniel.
Connection machine lisp: fine-grained parallel symbolic processing.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 279--297.
\bibitem{LISP-ON-A-REDUCED-INSTRUCTION-SET-PROCESSOR}
Steenkiste, Peter, and Hennessy, John.
{L}isp on a reduced-instruction-set-processor.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 192--201.
\bibitem{SEMANTIC-THEORY-FOR-EQUATIONAL-PROGRAMMING-LANGUAGES}
Thatte, Satish R.
Towards a semantic theory for equational programming languages.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 332--342.
\bibitem{LAWS-IN-MIRANDA}
Thompson, Simon.
Laws in {M}iranda.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 1--12.
\bibitem{MYSTERY-OF-THE-TOWER-REVEALED}
Wand, Mitchell, and Friedman, Daniel P.
The mystery of the tower revealed: a non-reflective description of the reflective tower.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 298--307.
\bibitem{RECONFIGURABLE-RETARGETABLE-BIGNUMS}
White, Jon L.
Reconfigurable, retargetable bignums: a case study in efficient, portable {L}isp system building.
In {\it Proc. 1986 ACM Conference on Lisp and Functional Programming}.
ACM SIGPLAN/SIGACT/SIGART (Cambridge, Massachusetts, August 1986), 174--191.
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Date: Sat 23 Aug 86 20:37:17-EDT
From: "Gerald Jay Sussman" <GJS%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>
Subject: Re: numbers
To: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
cc: rrrs-authors@MC.LCS.MIT.EDU
In-Reply-To: <8608210013.AA03947@tekchips.TEK>
Message-ID: <12233218691.23.GJS@OZ.AI.MIT.EDU>
The real numbers committee met today (all C of us, but we are not sure
if C=2↑Aleph0) in closed session!. We commend you, David Bartley and
Norm Adams for noticing our grievous errors and we thank you for the
nice suggestions. We move that suggestions 1-5 be immediately
adopted. Suggestion 6, concerning the syntax of exact/inexact
numerical constants is still not clear. What is your favorite
proposal anyway?
-------
∂25-Aug-86 2008 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@CSNET-RELAY.ARPA Another nit; my favorite numbers
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To: rrrs-authors@MC.LCS.MIT.EDU, jar@MC.LCS.MIT.EDU
Subject: Another nit; my favorite numbers
In-Reply-To: Your message of Sat 23 Aug 86 20:37:17-EDT.
<12233218691.23.GJS@OZ.AI.MIT.EDU>
Date: 25 Aug 86 14:29:47 PDT (Mon)
From: willc%tekchips.tek.csnet@CSNET-RELAY.ARPA
The description of map in section 6.9 says that its first argument must
be a procedure of one argument. The description should say instead
that "The {\it list}s must be lists, and {\it proc} must be a procedure
taking as many arguments as there are {\it list}s."
----------------------------------------------------------------
Gerry asked what my favorite proposal was for the implicit exactness
of numeric constants. It is:
1. Constants of the form x+yi, x-yi, and x@y are exact iff both x
and y are exact as real constants.
2. Constants of the form x/y are exact iff both x and y are exact
as integer constants and there is no explicit prefix that says
otherwise.
3. Constants that contain sharp signs to indicate imprecise digits
are inexact unless there is an explicit prefix that says
otherwise.
4. Constants that contain a nonempty exponent suffix are exact iff
they are exact after shifting the decimal point and/or adding
zeroes to eliminate the exponent. (For example, 1.1e6 would
be treated as 1100000, 40e-3 would be treated as .040, 2/3e2
would be treated as 200/3, and 2/3e-2 would be treated as 2/300.)
5. Constants that contain a decimal point but no exponent or sharp
signs indicating imprecise digits are exact iff there are no
digits to the right of the decimal point and there is no explicit
prefix that says otherwise.
6. Constants that contain no decimal point, exponent, or sharp
signs indicating imprecise digits are exact iff there is no
explicit prefix that says otherwise.
Whew! Rule 4 is probably the most controversial, followed by rule 5.
peace, Will
∂28-Aug-86 0849 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU Minutes from lunch 5 August 1986
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Date: 28 Aug 1986 11:11 EDT (Thu)
Message-ID: <JINX.12234426370.BABYL@MIT-OZ>
From: Bill Rozas <JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>
To: willc%tekchips.tek.csnet@RELAY.CS.NET
Cc: rrrs-authors@MC.LCS.MIT.EDU
Subject: Minutes from lunch 5 August 1986
In-reply-to: Msg of 14 Aug 1986 16:00-EDT from willc%tekchips.tek.csnet at CSNET-RELAY.ARPA
Wow! we have a full schedule ahead. Given the amount of flame which
just agreeing on the language has generated, I can imagine what trying
to agree on these issues will cause. I definitely look forward to it.
Something we might also think about standarizing is graphics
primitives. I realize this is hardware/system dependent, but it is
probably no harder than agreeing on interrupts and similar things.
It would be nice if simple graphics programs were also portable.
∂28-Aug-86 0908 @MC.LCS.MIT.EDU:mhwu%hplmhw@hplabs.HP.COM Minutes/Standardize Graphics
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Date: Thu, 28 Aug 86 09:02:41 pdt
From: Henry M. Wu <mhwu%hplmhw@hplabs.HP.COM>
Message-Id: <8608281602.AA00425@hplmhw>
To: JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU
Cc: willc%tekchips.tek.csnet@RELAY.CS.NET, rrrs-authors@MC.LCS.MIT.EDU
In-Reply-To: Bill Rozas's message of 28 Aug 1986 11:11 EDT (Thu)
Subject: Minutes/Standardize Graphics
One comment I have heard from talking to people around here is that
they are surprised Scheme is trying put everything into the language
specs rather than define libraries (like C, I guess).
I'm not claiming this is the right thing, but it does seem like
something worth pondering.
Henry
∂28-Aug-86 2012 @MC.LCS.MIT.EDU:GJS%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU Re: Minutes from lunch 5 August 1986
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Date: Thu 28 Aug 86 14:21:58-EDT
From: "Gerald Jay Sussman" <GJS%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>
Subject: Re: Minutes from lunch 5 August 1986
To: JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU, rrrs-authors@MC.LCS.MIT.EDU
In-Reply-To: <JINX.12234426370.BABYL@MIT-OZ>
Message-ID: <12234461088.59.GJS@OZ.AI.MIT.EDU>
I disagree that it is good to mix graphics in with other things.
I think that graphics is pretty poorly understood and rather idiosyncratic --
it will just cause lots of wasted flamage to work on that.
-------
∂29-Aug-86 1503 @MC.LCS.MIT.EDU:andy@ads.ARPA graphics for Scheme
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Date: Fri, 29 Aug 86 06:41:16 pdt
From: andy@ads.ARPA (Andy Cromarty)
To: rrrs-authors@mit-mc.ARPA
Subject: graphics for Scheme
A good alternative to providing graphics capability is to solve the
more general problem of designing a clean foreign function interface
standard. This would permit a variety of useful existing software
packages to be integrated into Scheme environments without requiring
that we deflect our attention from substantive language design issues
(and our plate is rather full already) to address ancillary and difficult
problems such as design of packages for graphics, window systems, etc.
This would also make Scheme much more attractive to people who actually
want to use Scheme as a programming language rather than as an object
of study.
Designing a good foreign function interface is nontrivial if we
wish to maintain a principled design approach. I suspect that
it would require us to revisit some of the thorny problems we've
brushed up against but not really solved in the past few months,
such as whether Scheme should be thought of as having a dynamic
binding environment vs. an essentially static one defined purely
by the lexical structure of our programs. In the former case,
a relatively conventional dynamic loading scheme might work best;
for the latter case, a declaration-based system might be more
appropriate. In either case, we would need a spec for translating
Scheme data structures into those of other languages. (Perhaps
the SUN xdr might be a good spec to work from for this part of
the problem.)
A foreign function interface might also make Scheme a better
base language environment for studying some difficult contemporary
programming paradigm problems, such as techniques for distributed
and parallel processing. Currently we achieve this locally at ADS by
extending our Scheme with functions written in C and linked in
statically by the linkage editor. This has the disadvantage of
requiring that the researcher know not only how to code the new
parallelism/distributed processing primitives, but also what the
internal structure of the Scheme environment is in some detail.
A foreign function interface would provide a sort of firewall that
would prevent the designer of new constructs from having to know
what the Scheme implementation's internals look like.
asc
∂02-Sep-86 1519 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU substring-vector-null-fill!, colitis, etc.
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Date: Tue, 2 Sep 86 18:19:59 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: substring-vector-null-fill!, colitis, etc.
To: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].90180.860902.JAR>
Here are changes I've made at the requests of people too numerous to
mention (I wish I could acknowledge everyone individually, but time
presses):
I've flushed SUBSTRING-FILL! and STRING-NULL?. If STRING-NULL? is
retained then VECTOR-NULL? should be added. These are both in a
somewhat different class than NULL? since NULL? is often used to
terminate recusrions but STRING- and VECTOR-NULL? aren't.
It's now clearly an error to alter an object returned as the value of a
constant expression, e.g. (string-set! "foo" 1 #\x) and (set-car! '(a b) 'c)
are errors.
The list of extended alphabetics has been moved from "other notations"
to "identifiers".
I'll try to flush the garbage about immutability from the eqv? section,
and leave the question of (eq? '(a) '(a)) unbreached.
Small organizational error fixed: the nonterminal <sequence expression>
is gone, and (begin <sequence>) is now an alternative right-hand side
for <derived expression>.
The equation defining exponentiation has been repaired.
-----
Questions:
- Advice sought on what to do about the grammar for COND and CASE. In
question is the treatment of non-final ELSE clauses. Two people have
mentioned that as it stands the grammar is too liberal. Should I change
it so that there are two rules for each, viz.
<derived expression> --> ...
| (cond <cond clause>+)
| (cond <cond clause>* (else <sequence>))
| ...
| (case <key> <case clause>+)
| (case <key> <case clause>* (else <sequence>))
| ...
? Seems to me it's not grave if it's left as is, since the text
explains that actually the else clause should come at the end.
- I can sort of see why VECTOR-FILL! exists (it has to exist internally in
any case, in order to support the optional argument), but symmetry
considerations would suggest either flushing it or adding STRING-FILL!.
Opinions? No change here so far.
- I don't think I have time to change number syntax, although I think
specifying default exactness on input is easier, since I can just copy
text from Will's messages. I have two small arguments with Will's rule
which says that 1e3 is exact. One is that this makes exactness somewhat
tricky to determine -- you have to be able to count in order to
determine whether a string represents an exact number or not. I prefer
the simpler rurule which says that the presence of an exponent marker
makes the number inexact by default. The second argument stems from CL
compatibility concerns: if Scheme's exact integers are identical to CL's
integers, and Scheme's inexact (rational) flonums are identical to CL's
flonums, then making 1e3 represent an exact number would be an
incompatibility between Scheme and CL. This correspondence seems
natural to me. I'd like to hear arguments in favor of Will's rule.
- I'm inclined to demote colon from alphabetic to unspecified (like \ and
|), although I'd like the case to be made more clearly. I would really
hate to see someone add Common-Lisp-like read-time packaging to any
Scheme, so I don't admit that as a good reason for this change, although
if foo:bar read in the same as (access bar foo) that wouldn't be so bad.
However, I'm primarily a Scheme-in-Common-Lisp user myself these days,
and the implementation and its integration into the host CL would indeed
be cleaner if colon weren't extended alphabetic, so I DO see CL
compatibility as a good reason for the change.
On the side of an alphabetic colon, I should mention that the
moderate-sized community of pro-Scheme people raised on Riesbeck,
Charniak, and/or McDermott's book(s), or otherwise immersed in Yale AI
Lisp culture, use colon pretty heavily as an alphabetic character.
Also, there are some other alternatives for CL <--> Scheme communication:
- A way to coerce packages to environments, so e.g. if you want
Lisp's ELT function you can say (access elt lisp-package). This is
what CLSCH does now.
- A procedure which makes Lisp symbols, e.g. (make-lisp-symbol 'lisp
'elt).
- A reader syntax such as #[Lisp-symbol lisp elt] or #>Lisp>elt.
None of these is quite as attractive as just saying lisp:elt.
I'll wait for more comments, then flip a coin.
- Jonathan
∂03-Sep-86 0424 @MC.LCS.MIT.EDU:ramsdell%faron@mitre-bedford.ARPA call-with-xxput-port
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Date: Wed, 3 Sep 86 07:17:30 edt
From: John D. Ramsdell <ramsdell%faron@mitre-bedford.ARPA>
Posted-Date: Wed, 3 Sep 86 07:17:30 edt
Message-Id: <8609031117.AA03165@faron.MENET>
To: rrrs-authors%mc.lcs.mit.edu@mitre-bedford.ARPA
Subject: call-with-xxput-port
Please do not forget the change associated with
call-with-input-port and call-with-output-port.
I suggest changing the names of no other I/O routines.
John
∂03-Sep-86 0625 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU substring-vector-null-fill!, colitis, etc.
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Date: 3 Sep 1986 09:02 EDT (Wed)
Message-ID: <JINX.12235975868.BABYL@MIT-OZ>
From: Bill Rozas <JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>
To: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Cc: rrrs-authors@MC.LCS.MIT.EDU
Subject: substring-vector-null-fill!, colitis, etc.
In-reply-to: Msg of 2 Sep 1986 18:19-EDT from Jonathan A Rees <JAR at AI.AI.MIT.EDU>
1) I vote to change the grammar to only allow the final ELSE case.
It does not seem like a very large change.
2) VECTOR-FILL! and STRING-FILL! are completely symmetric. They both
must exist internally for the MAKE-STRING and MAKE-VECTOR procedures.
FLush both or keep both, but I vote to flush both since they can be
written using VECTOR-SET! and STRING-SET!
3) I think that except in a few cases, it is not necessary to agree on
default exactness in the number syntax. Anybody who is going to use
advantage of it (whenever somebody implements it), will certainly want
to force the exactness/inexactness of his/her explicit numerals by
using prefixes, and nobody else will care, probably.
The only case that must be decided, in my opinion, is making things
like 3, 123, -456 ("obvious" integers) exact, so they can be used as
indeces to VECTOR-MUMBLE and STRING-MUMBLE.
Thus some implementations could agree to be compatible with CL, and
some to take a completely different approach, but the most common case
(and needed by non-numeric code) would be compatible.
4) I like alphabetic colon, and dislike the CL package system too, but
giving up colon seems like a very minor issue. There are too many
people trying to make a dual CL/Scheme environment, and we should not
make this job harder than it has to be. Thus I vote moving colon to
unspecified.
∂04-Sep-86 0858 @MC.LCS.MIT.EDU:F95THOMP%CARLETON.BITNET@WISCVM.WISC.EDU Scheme Books?
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From: DAVE THOMAS <F95THOMP%CARLETON.BITNET@WISCVM.WISC.EDU>
To: <scheme@MC.LCS.MIT.EDU>
Subject: Scheme Books?
What books are available for Scheme(other than S&ICP)?
Are there solution manuals available for any of these?
Thanks
∂04-Sep-86 1828 @MC.LCS.MIT.EDU:wecker%cookie.DEC@decwrl.DEC.COM Please delete me from this distribution list, thanks - dave
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From: wecker%cookie.DEC@decwrl.DEC.COM (DAVE TANSTAAFL WECKER)
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Subject: Please delete me from this distribution list, thanks - dave
∂05-Sep-86 1947 @MC.LCS.MIT.EDU:mh@BU-CS.BU.EDU list
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Subject: list
Could you please delete me from the distribution list. Thank you.
∂08-Sep-86 0330 @MC.LCS.MIT.EDU:shneider%cui.unige.chunet%ubc.csnet@CSNET-RELAY.ARPA Beginners question: Advising methods in TI scheme
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To: scheme@MC.LCS.MIT.EDU
MMDF-Warning: Parse error in original version of preceding line at CSNET-RELAY.ARPA
Message-Id: <121:shneider@cui.unige.chunet>
Subject: Beginners question: Advising methods in TI scheme
1) I started writing a program with lots of methods. Now it start loosing
"track".
-> How can I trace methods in Ti scheme?
i.e. is there an elegant way of doing it ?
2) Is there any person to whom I should send this kind of request ?
Thanks for any help
(and reply by e-mail)
-------------------------------------------------------------------------------
Daniel K.Schneider
Departement de science politique, Universite de Geneve
1211 GENEVE 4 (Switzerland), Tel. (..41) 22 20 93 33 ext. 2357
to VMS/BITNET: to UNIX/EAN (preferable):
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∂08-Sep-86 0826 @MC.LCS.MIT.EDU:philbin-jim@YALE.ARPA Re: [THOMAS: Scheme Books?]
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From: James F Philbin <philbin-jim@YALE.ARPA>
Message-Id: <8609081501.AA17146@Yale-Bulldog.YALE.ARPA>
Subject: Re: [THOMAS: Scheme Books?]
To: <Scheme@MC.LCS.MIT.EDU>
What books are available for Scheme ? Are there solution manuals
available for any of these?
Steven Slade had written and introductory programming book which
might be of interest. Contact SLADE@YALE for details.
- Jim
The T Programming Language: A Dialect of LISP
Stephen Slade
Prentice-Hall, Englewood Cliffs, N.J.
To appear: November, 1986
∂08-Sep-86 0848 @MC.LCS.MIT.EDU:carr%utah-orion@utah-cs.arpa scoops
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From: carr%utah-orion@utah-cs.arpa (Harold Carr)
Message-Id: <8609081532.AA03156@utah-orion.ARPA>
To: scheme@mc.lcs.mit.edu
Subject: scoops
Could someone tell me how to obtain SCOOPS?
Thanks, Harold
∂08-Sep-86 1334 @MC.LCS.MIT.EDU:shneider%cui.unige.chunet%ubc.csnet@CSNET-RELAY.ARPA Beginners question: Advising methods in TI scheme
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To: scheme@MC.LCS.MIT.EDU
MMDF-Warning: Parse error in original version of preceding line at CSNET-RELAY.ARPA
Message-Id: <122:shneider@cui.unige.chunet>
Subject: Beginners question: Advising methods in TI scheme
1) I started writing a program with lots of methods. Now it start loosing
"track".
-> How can I trace methods in Ti scheme?
i.e. is there an elegant way of doing it ?
2) Is there any person to whom I should send this kind of request ?
Thanks for any help
(and reply by e-mail)
-------------------------------------------------------------------------------
Daniel K.Schneider
Departement de science politique, Universite de Geneve
1211 GENEVE 4 (Switzerland), Tel. (..41) 22 20 93 33 ext. 2357
to VMS/BITNET: to UNIX/EAN (preferable):
BITNET: SCHNEIDER@CGEUGE51 shneider%cui.unige.chunet@CERNVAX
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∂08-Sep-86 1509 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Good & bad news
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Date: Mon, 8 Sep 86 18:11:24 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: Good & bad news
To: rrrs-authors@MC.LCS.MIT.EDU
cc: slade@YALE.ARPA, meehan@YALE.ARPA
Message-ID: <[AI.AI.MIT.EDU].92170.860908.JAR>
The good news is that the scheme report is in the mail, and the editor
of SIGPLAN Notices will have it within a couple of days.
The bad news is that the November issue of SIGPLAN, like the October
issue, is devoted to conference proceedings for some conference or
other. So there is no room for the Scheme report.
Barring other unforeseen catastrophes, it will be in the December issue.
A few people have asked me whether page numbers are known, and I expect
they won't be until known until mid-December. I suggest calling Dick
Wexelblat on the phone around that time if you really want to know.
We plan to print this version as an MIT AI memo. I'll make the LaTeX
sources available on MIT-PREP sometime this week.
I'll also US mail hardcopy to the authors. If the Indiana CS department
is interested in issuing it as a new tech report, I'd be happy to mail a
magnetic tape with the sources & DVI file.
Jonathan
∂08-Sep-86 1614 @MC.LCS.MIT.EDU:wagle%iuvax.indiana.edu@CSNET-RELAY.ARPA substring-vector-null-fill!, coliti
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Date: Mon, 8 Sep 86 13:10:49 est
From: Perry Wagle <wagle%iuvax.indiana.edu@CSNET-RELAY.ARPA>
To: rrrs-authors%mit-mc.CSNET@CSNET-RELAY.ARPA
Subject: substring-vector-null-fill!, coliti
If |(set-car! '(a b) 'c)| is an error, how about |(set-car! '(d e) 'f)|?
That is, when do backquoted expressions denote constants? (I vote never).
[A related question is whether |`(d e)| returns the same list each time it
is executed. I suspect you may want to table the above paragraph.]
Vectors have constant length. Strings have variable length. With this
view it would make sense to "fill" a vector, but not a string.
Perry Wagle, Indiana University, Bloomington Indiana.
...!ihnp4!inuxc!iuvax!wagle (USENET)
wagle@indiana (CSNET)
wagle%indiana@csnet-relay (ARPA)
∂08-Sep-86 2212 @MC.LCS.MIT.EDU:asrivast%tilde%ti-csl.csnet@CSNET-RELAY.ARPA Advising methods in TI Scheme
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Date: Mon, 8 Sep 86 15:25:20 cdt
From: Amitabh Srivastava <asrivast%tilde%ti-csl.csnet@CSNET-RELAY.ARPA>
To: schneider%cui.unige.chunet%ubc@CSNET-RELAY.ARPA
Subject: Advising methods in TI Scheme
Cc: scheme%mc.lcs.mit.edu@CSNET-RELAY.ARPA
>> 1) I started writing a program with lots of methods. Now it start loosing
>> "track".
>> -> How can I trace methods in Ti scheme?
>> i.e. is there an elegant way of doing it ?
The procedure %sc-method-env returns the environment containing
the methods of a class. By using this and advise-entry and advise-exit
different tracing macros can be written.
For example, we can write a special form trace-method-entry to trace
the entry of method m1 of class class1.
(trace-method-entry m1 class1)
=>
(macro trace-method-entry
(lambda (e)
(let ((method (cadr e))
(class (caddr e)))
`(ADVISE-ENTRY
(ACCESS ,method (%sc-method-env ,class))
(lambda (p a e)
(writeln " The method " ',method " of class " ',class
" is called with " a))))))
Similarly one can write a macro to trace exits.
- amitabh
∂09-Sep-86 0429 @MC.LCS.MIT.EDU:ramsdell%faron@mitre-bedford.ARPA Slade's book in bib?
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Date: Tue, 9 Sep 86 07:21:18 edt
From: John D. Ramsdell <ramsdell%faron@mitre-bedford.ARPA>
Posted-Date: Tue, 9 Sep 86 07:21:18 edt
Message-Id: <8609091121.AA17988@faron.MENET>
To: rrrs-authors%mc.lcs.mit.edu@mitre-bedford.ARPA
Subject: Slade's book in bib?
Maybe Stephen Slade's book on T should be added to
the r↑3rs bibliography. Would some one with access
to it, make a recommendation?
John
∂13-Sep-86 2054 @MC.LCS.MIT.EDU:fowler@rochester.arpa Re: Prolog in Scheme?
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Date: Sat, 13 Sep 86 23:11:43 edt
From: Rob Fowler <fowler@rochester.arpa>
To: scheme@MC.LCS.MIT.EDU, MWILSON%CARLETON.BITNET@WISCVM.WISC.EDU
Cc: Rob Fowler <fowler@rochester.arpa>
Subject: Re: Prolog in Scheme?
If you get any responses I'd appreciate it if you could pass them along to
me. I'm currently teaching an "AI Programming" course entirely in Scheme
using MacScheme and I'd really like to get hld of a Prolog or even a subset
that I could turn the students loose on for a couple of weeks.
-- Rob Fowler (fowler@rochester.edu)
∂14-Sep-86 0204 @MC.LCS.MIT.EDU:MWILSON%CARLETON.BITNET@WISCVM.WISC.EDU Prolog in Scheme?
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Date: 08 Sep 86 15:49:00 EDT
From: Mike Wilson <MWILSON%CARLETON.BITNET@WISCVM.WISC.EDU>
To: <scheme@MC.LCS.MIT.EDU>
Subject: Prolog in Scheme?
Hello,
Are there any implementations of Prolog written in Scheme? I'm
interested in any and all versions from minimal to full-featured.
.Mike
∂15-Sep-86 0450 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Prolog in Scheme?
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Date: Sun, 14 Sep 86 12:34:06 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: Prolog in Scheme?
To: fowler@ROCHESTER.ARPA
cc: MWILSON%CARLETON.BITNET@WISCVM.WISC.EDU, scheme@MC.LCS.MIT.EDU
In-reply-to: Msg of Sat 13 Sep 86 23:11:43 edt from Rob Fowler <fowler at rochester.arpa>
Message-ID: <[AI.AI.MIT.EDU].93903.860914.JAR>
Date: Sat, 13 Sep 86 23:11:43 edt
From: Rob Fowler <fowler at rochester.arpa>
If you get any responses I'd appreciate it if you could pass them along to
me. I'm currently teaching an "AI Programming" course entirely in Scheme
using MacScheme and I'd really like to get hld of a Prolog or even a subset
that I could turn the students loose on for a couple of weeks.
Why not just use the query system in Structure & Interpretation?
- Jonathan
∂15-Sep-86 1223 @MC.LCS.MIT.EDU:ramsdell%faron@mitre-bedford.ARPA Begin in the Formal Semantics
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Date: Mon, 15 Sep 86 15:15:40 edt
From: John D. Ramsdell <ramsdell%faron@mitre-bedford.ARPA>
Posted-Date: Mon, 15 Sep 86 15:15:40 edt
Message-Id: <8609151915.AA16806@faron.MENET>
To: rrrs-authors%mc.lcs.mit.edu@mitre-bedford.ARPA
Subject: Begin in the Formal Semantics
Begin is described in the abstract syntax, but there is
no semantic function for it. Later, on page 35, the
semantics of begin is given under the derived expression
types heading. Should begin be described in the abstract
syntax section?
John
∂15-Sep-86 1237 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Begin in the Formal Semantics
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From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: Begin in the Formal Semantics
To: ramsdell%faron@MITRE-BEDFORD.ARPA
cc: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Mon 15 Sep 86 15:15:40 edt from John D. Ramsdell <ramsdell%faron at mitre-bedford.ARPA>
Message-ID: <[AI.AI.MIT.EDU].94273.860915.JAR>
Date: Mon, 15 Sep 86 15:15:40 edt
From: John D. Ramsdell <ramsdell%faron at mitre-bedford.ARPA>
To: rrrs-authors%mc.lcs.mit.edu at mitre-bedford.ARPA
Re: Begin in the Formal Semantics
Organization: The MITRE Corp., Bedford, MA
Posted-Date: Mon, 15 Sep 86 15:15:40 edt
Message-Id: <8609151915.AA16806@faron.MENET>
Begin is described in the abstract syntax, but there is
no semantic function for it. Later, on page 35, the
semantics of begin is given under the derived expression
types heading. Should begin be described in the abstract
syntax section?
It should be flushed from the abstract syntax. I intended to do this
but only partially succeeded.
Jonathan
∂15-Sep-86 1243 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Begin in the Formal Semantics
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From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: Begin in the Formal Semantics
To: ramsdell%faron@MITRE-BEDFORD.ARPA
cc: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].94274.860915.JAR>
Date: Mon, 15 Sep 86 15:15:40 edt
From: John D. Ramsdell <ramsdell%faron at mitre-bedford.ARPA>
To: rrrs-authors%mc.lcs.mit.edu at mitre-bedford.ARPA
Re: Begin in the Formal Semantics
Organization: The MITRE Corp., Bedford, MA
Posted-Date: Mon, 15 Sep 86 15:15:40 edt
Message-Id: <8609151915.AA16806@faron.MENET>
Begin is described in the abstract syntax, but there is
no semantic function for it. Later, on page 35, the
semantics of begin is given under the derived expression
types heading. Should begin be described in the abstract
syntax section?
It should be flushed from the abstract syntax. I intended to do this
but only partially succeeded.
Jonathan
∂15-Sep-86 1910 @MC.LCS.MIT.EDU:asrivast%tilde%ti-csl.csnet@CSNET-RELAY.ARPA Advising methods in TI Scheme
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From: Amitabh Srivastava <asrivast%tilde%ti-csl.csnet@CSNET-RELAY.ARPA>
To: scheme%mc.lcs.mit.edu@CSNET-RELAY.ARPA
Subject: Advising methods in TI Scheme
Cc: shneider%cui.unige.chunet%ubc.csnet@CSNET-RELAY.ARPA
>> 1) I started writing a program with lots of methods. Now it start loosing
>> "track".
>> -> How can I trace methods in Ti scheme?
>> i.e. is there an elegant way of doing it ?
The procedure %sc-method-env returns the environment containing
the methods of a class. By using this and advise-entry and advise-exit
different tracing macros can be written.
For example, we can write a special form trace-method-entry to trace
the entry of method m1 of class class1.
(trace-method-entry m1 class1)
=>
(macro trace-method-entry
(lambda (e)
(let ((method (cadr e))
(class (caddr e)))
`(ADVISE-ENTRY
(ACCESS ,method (%sc-method-env ,class))
(lambda (p a e)
(writeln " The method " ',method " of class " ',class
" is called with " a))))))
Similarly one can write a macro to trace exits.
- amitabh
∂17-Sep-86 1224 @MC.LCS.MIT.EDU:prlb2!vauclair@seismo.CSS.GOV Request for information on new releases.
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Subject: Request for information on new releases.
Organisation: Philips Research Laboratory Brussels, Belgium
Uucp-From: mvauclair@prlb2.UUCP
Date: 17 Sep 86 17:24:35 N (Wed)
From: Marc Vauclair <prlb2!vauclair@seismo.CSS.GOV>
First, sorry for sending this request to scheme@mit-mc instead of
scheme-team@mit-mc but when trying the last address I got the message
reproduced at the end of this one.
For more than a year by now, we are using the MIT Scheme implementation
(Microcode version 6.1, Runtime version 11.2) on our Vax with Unix 4.2. In few
words, we greatly appreciate both the language and its implementation. There
are only two dark spots :
- the lack of documentation of the implementation (the only
documentation I have at my disposition are the "Structure and
Interpretation..." book and the revised revised report
- the slowness of the terminal i/o and in some circumstances of the
interpreter itself.
Is a newer version for VAX Unix available ? Does it include a compiler ? Is a
version for SUN 3 available ? How can we get these new versions ? Is it
possible to get some documentation on the implementation ?
Regards,
Marc.
[*][*][*][*][*][*][*][*][*][*][*][*][*][*][*][*][*][*][*][*][*][*][*][*][*]
From: Communications Satellite <seismo!MC.LCS.MIT.EDU!COMSAT>
Subject: Msg of Wednesday, 17 September 1986 06:35-EDT
To: "prlb2!vauclair@seismo.CSS.GOV"
Message-Id: <[MC.LCS.MIT.EDU].88830.860917>
============ A copy of your message is being returned, because: ============
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Subject: Request for information on new releases.
Organisation: Philips Research Laboratory Brussels, Belgium
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Date: 17 Sep 86 11:27:54 N (Wed)
From: Marc Vauclair <prlb2!vauclair@seismo.CSS.GOV>
∂22-Sep-86 1441 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Revised↑3 Report on Scheme
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Date: Mon, 22 Sep 86 17:39:42 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: Revised↑3 Report on Scheme
To: scheme@MC.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].97185.860922.JAR>
Announcement:
The "Revised↑3 Report on the Algorithmic Language Scheme" has been
completed. It is an updated version of the "Revised Revised Report on
Scheme" which appeared in summer 1985. A draft of this report was
circulated at the Lisp and Functional Programming Conference last month;
the final version is practically the same as that draft.
The "Revised↑3 Report" will appear in SIGPLAN notices in December of
this year. It will also be printed as MIT AI Memo 848a and as an
Indiana University CSD technical report. I'll send a separate message
as soon as I receive ordering information from MIT's publications
office, so everyone who wants one can get one.
- Jonathan Rees
∂24-Sep-86 0739 @MC.LCS.MIT.EDU:DLW@ALDERAAN.SCRC.Symbolics.COM [MWILSON%CARLETON.BITNET@WISCVM.WISC.EDU: Prolog in Scheme?]
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Date: Wed, 24 Sep 86 10:36 EDT
From: Daniel L. Weinreb <DLW@ALDERAAN.SCRC.Symbolics.COM>
Subject: [MWILSON%CARLETON.BITNET@WISCVM.WISC.EDU: Prolog in Scheme?]
To: Scheme@MIT-MC.ARPA
In-Reply-To: <860915140445.8.SGR@GROUSE.SCRC.Symbolics.COM>
Message-ID: <860924103627.1.DLW@CHICOPEE.SCRC.Symbolics.COM>
Date: Mon, 15 Sep 86 14:04 EDT
From: Stephen G. Rowley <SGR@STONY-BROOK.SCRC.Symbolics.COM>
Answers, if any, to the Scheme mailing list at MIT:
Date: 08 Sep 86 15:49:00 EDT
From: Mike Wilson <MWILSON%CARLETON.BITNET@WISCVM.WISC.EDU>
To: <scheme@MC.LCS.MIT.EDU>
Subject: Prolog in Scheme?
Hello,
Are there any implementations of Prolog written in Scheme? I'm
interested in any and all versions from minimal to full-featured.
.Mike
It would likewise be interesting to know if there are any versions of
Scheme written in Prolog.
∂24-Sep-86 0936 @MC.LCS.MIT.EDU:searfus@lll-icdc.arpa please add me ...
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Date: 24 Sep 86 07:50:00 PDT
From: "Searfus, Robert" <searfus@lll-icdc.arpa>
Subject: please add me ...
To: "scheme" <scheme@mc.lcs.mit.edu>
Reply-To: "Searfus, Robert" <searfus@lll-icdc.arpa>
to the scheme mailing list.
<bob> searfus@lll-icdc.arpa
------
∂25-Sep-86 0750 @MC.LCS.MIT.EDU:TIM@cis.upenn.edu prolog in scheme
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Posted-Date: Thu, 25 Sep 86 09:42 EDT
Message-Id: <8609251352.AA02609@linc.cis.upenn.edu>
From: Tim Finin <Tim@cis.upenn.edu>
Subject: prolog in scheme
To: scheme@mc.lcs.mit.edu
Date: Thu, 25 Sep 86 09:42 EDT
We tried using the query system in "Structure & Interpretation" in our
freshman class last year and found it wanting in some respects. (1) It
doesn't handle disjunctions unless the disjuncts contain the same variables.
(2) It is extremely slow. We were using it in TI's PC Scheme on AT's. We
gave some very simple logic programming problems (e.g. the standard kinship
relations) and found that the students we spending 10 or 15 minutes waiting
for the query system to finish! They found this very frustrating.
I'd think I would like to cover the query system from S&I in class because
it's clear and simple and have the students use a more suped-up version that
is reasonably efficient. In addition, facilities like "retract",
"reconsult", etc. would easy it's use in homeworks.
I'd also like to consider using a system which uses a prolog-like
depth-first backtracking search.
Tim
∂25-Sep-86 1309 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU prolog in scheme
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Date: 25 Sep 1986 13:27 EDT (Thu)
Message-ID: <JINX.12241791234.BABYL@MIT-OZ>
From: Bill Rozas <JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>
To: Tim Finin <Tim@CIS.UPENN.EDU>
Cc: scheme@MC.LCS.MIT.EDU
Subject: prolog in scheme
In-reply-to: Msg of 25 Sep 1986 09:42-EDT from Tim Finin <Tim at cis.upenn.edu>
We tried using the query system in "Structure & Interpretation" in our
freshman class last year and found it wanting in some respects. (1) It
doesn't handle disjunctions unless the disjuncts contain the same variables.
(2) It is extremely slow. We were using it in TI's PC Scheme on AT's. We
gave some very simple logic programming problems (e.g. the standard kinship
relations) and found that the students we spending 10 or 15 minutes waiting
for the query system to finish! They found this very frustrating.
(1) GJS consistently updates the query language and fixes versions as bugs
appear. You should get in touch with him, the bug may have been
fixed.
(2) I have observed this also on MacScheme. I don't know about PC
Scheme, but in the case of MacScheme the reason is probably that
streams have no interpreter support, they are written in scheme. This
is unlike MIT Scheme, for which the code was originally written. PC
Scheme may have the same problem. While it is not blindingly fast on
our machines at MIT, it only becomes slow with relatively complicated
programs, and is adequately fast for the class. 10 or 15 mins. is way
longer than I've ever seen it take while solving the S&ICP problems.
∂28-Sep-86 0818 @MC.LCS.MIT.EDU:jeff%aiva.edinburgh.ac.uk@Cs.Ucl.AC.UK Prolog in Scheme
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From: Jeff Dalton <jeff%aiva.edinburgh.ac.uk@Cs.Ucl.AC.UK>
Date: Sun, 28 Sep 86 16:04:02 -0100
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To: scheme@mc.lcs.mit.edu
Subject: Prolog in Scheme
Unfortunately, the query system in Structure and Interpretation is
not Prolog. In particular, it doesn't handle cut. While this
may not metter much to some (especially those who think cut should
be fluched anyway), it does make the system considerably
less interesting as an implementation of Prolog.
∂30-Sep-86 0507 @MC.LCS.MIT.EDU:ramsdell%linus@mitre-bedford.ARPA Refering to the Revised↑3 Report on Scheme
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From: John D. Ramsdell <ramsdell%linus@mitre-bedford.ARPA>
Posted-Date: Tue, 30 Sep 86 08:04:40 EDT
Message-Id: <8609301204.AA02723@linus.MENET>
To: scheme%mc.lcs.mit.edu@mitre-bedford.ARPA
Subject: Refering to the Revised↑3 Report on Scheme
I've seen "The Revised Revised Report on Scheme or
An UnCommon Lisp" referenced as "R3S". I would like
to discourage this and suggest using "RRRS" or "R2RS".
The "Revised↑3 Report on the Algorithmic Language Scheme"
will be in December SIGPLAN. The obvious reference is
"R3RS" which is why I would like to discourge the use
of "R3S" for the UnCommon Lisp report.
John
∂01-Oct-86 1416 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU R↑3RS sources
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Date: Wed, 1 Oct 86 15:44 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: R↑3RS sources
To: rrrs-authors@MC.LCS.MIT.EDU
cc: carr@UTAH-ORION.ARPA
Message-ID: <"861001154411.1.jar@AI"@ROCKY-GRAZIANO.LCS.MIT.EDU>
Those of you with Internet FTP capabilities should now be able to get
the report sources from MIT-PREP. Login as user scheme password scheme,
and get the file
/scheme/r3rs.tar
if you can use a unix tar file, otherwise get all the files in the
directory "/scheme/documentation/r3rs".
∂02-Oct-86 0803 @MC.LCS.MIT.EDU:GOERZ@SUMEX-AIM.ARPA Lost mail
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Date: Thu 2 Oct 86 07:56:36-PDT
From: Gunther Goerz <GOERZ@SUMEX-AIM.ARPA>
Subject: Lost mail
To: scheme@MC.LCS.MIT.EDU
cc: Goerz@SUMEX-AIM.ARPA
Message-ID: <12243598741.13.GOERZ@SUMEX-AIM.ARPA>
Unformtunately I made the big mistake to erase the SCHEME mail between
Aug. 4 and Sep. 30 before having read it. As completely.
As there were some very interesting items on the list, let me please
ask you whether there is a simple way to remail the stuff to me.
Sorry for the inconvenience, it was just my fault!
---Guenther
-------
∂02-Oct-86 1013 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Lost mail
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Date: Thu, 2 Oct 86 11:36:35 EDT
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: Lost mail
To: GOERZ@SUMEX-AIM.ARPA
cc: scheme@MC.LCS.MIT.EDU
In-reply-to: Msg of Thu 2 Oct 86 07:56:36-PDT from Gunther Goerz <GOERZ at SUMEX-AIM.ARPA>
Message-ID: <[AI.AI.MIT.EDU].101186.861002.JAR>
Use FTP. Connect to MIT-MC, use an arbitrary user name and password,
and get the file LSPMAI; SCHEME MAIL. (Note that the file name has
spaces in it.)
You can send questions like this to Scheme-Request@MC.
Jonathan
∂02-Oct-86 1114 @MC.LCS.MIT.EDU:mohammad%utah-orion@utah-cs.arpa Can anyone hear me?
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From: mohammad%utah-orion@utah-cs.arpa (Mohammad Pourheidari)
Message-Id: <8610021541.AA24813@utah-orion.ARPA>
To: scheme@mc.lcs.mit.edu
Subject: Can anyone hear me?
Hello, My name is Mohammad Pourheidari. I am a member of PASS group down
at the University of Utah. I have made a couple of attempts to get a hold of
Dr. Henry Lieberman; unfortunately both times unsuccessful. The net address
I have been using is : henry@mit-mc. Can anyone tell me whether this is the
best place to send him mail, or even better can anyone tell me what is the
best way to get a hold of him.
Thank you,
Mohammad
∂02-Oct-86 1714 @MC.LCS.MIT.EDU:zorn@kim.Berkeley.EDU I am interested in gathering `significant' Scheme programs...
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To: scheme@mc.lcs.mit.edu
Subject: I am interested in gathering `significant' Scheme programs...
Date: Thu, 02 Oct 86 17:07:57 PDT
From: Benjamin Zorn <zorn@kim.Berkeley.EDU>
My name is Ben Zorn, and I'm working on the SPUR Multiprocessor Lisp
system at UC Berkeley. My particular interest is multiprocessor
garbage collection. My current plans include taking `significant'
Scheme programs and studying the object manipulation behavior that
they have. By significant, I mean programs that are large enough to
generate reasonable amounts of garbage, and are also considered to be
important programs that are frequently used. Multiprocessor programs
would be of even more interest to me. If you have publically
available programs that would be of interest to me, I would greatly
appreciate hearing from you. I will make a list of the replies
available to this mailing list in a few weeks.
-Ben Zorn (zorn@kim.berkeley.edu)
∂06-Oct-86 2336 @MC.LCS.MIT.EDU:dan%umass-boston.csnet@CSNET-RELAY.ARPA SCHEME implementations
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Date: Mon, 6 Oct 86 17:01:38 edt
From: Dan Stefanescu <dan%umass-boston.csnet@CSNET-RELAY.ARPA>
To: scheme%MC.LCS.MIT.EDU@RELAY.CS.NET
Subject: SCHEME implementations
Cc: dan@UMASS-BOSTON.CSNET
Are there any for AT&T hardware, in particular for UNIX PC's and
AT&T 3B2-400 machines ? Any pointers will be greatly appreciated.
Dan
∂15-Oct-86 0606 @MC.LCS.MIT.EDU:ramsdell%faron@mitre-bedford.ARPA Object-Oriented Schemes
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Date: Wed, 15 Oct 86 08:51:14 edt
From: John D. Ramsdell <ramsdell%faron@mitre-bedford.ARPA>
Posted-Date: Wed, 15 Oct 86 08:51:14 edt
Message-Id: <8610151251.AA01933@faron.MENET>
To: scheme%mc.lcs.mit.edu@mitre-bedford.ARPA
Subject: Object-Oriented Schemes
Cc: ramsdell@mitre-bedford.ARPA
I am wondering if people on this list would
like to discuss Object-Oriented Schemes.
Three implementations come to mind at this time.
The oldest I know about is T[1]. TI has put its
Object-Oriented system called SCOOPS in the public
domain, as is T. I have had no experience with
SCOOPS. Oaklisp[2] adds to the T idea of first
class objects and operations, the idea of first
class types. I'm not sure what this contributes.
Are there any other implementations you would
like to discuss?
John
[1] Rees, J. & N. Adams IV, "T: a dialect of Lisp or,
Lambda: the ultimate software tool", 1982 Lisp and
Functional Programming, August 1982.
[2] Lang, K. & B. Pearlmutter, "Oaklisp: an
Object-Oriented Scheme with First Class Types",
OOPSLA '86, Sep-Oct 1986.
∂16-Oct-86 1410 @MC.LCS.MIT.EDU:jeff%aiva.edinburgh.ac.uk@Cs.Ucl.AC.UK Public Domain
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From: Jeff Dalton <jeff%aiva.edinburgh.ac.uk@Cs.Ucl.AC.UK>
Date: Thu, 16 Oct 86 19:43:23 -0100
Message-Id: <5570.8610161843@aiva.ed.ac.uk>
To: scheme@mc.lcs.mit.edu
Subject: Public Domain
Date: Wed, 15 Oct 86 08:51:14 edt
From: "John D. Ramsdell" <ramsdell%faron@arpa.mitre-bedford>
To: scheme <scheme%edu.mit.lcs.mc@arpa.mitre-bedford>
Subject: Object-Oriented Schemes
I am wondering if people on this list would
like to discuss Object-Oriented Schemes.
Three implementations come to mind at this time.
The oldest I know about is T[1]. TI has put its
Object-Oriented system called SCOOPS in the public
domain, as is T.
Well, I would like to discuss such things, but what I'd like to know
at the moment is this: is T now in the public domain? How might I
obtain a copy of it or of SCOOPS.
I'm sorry if this isn't the proper forum for such questions, but
my options seem somewhat limited from here.
-- Jeff
P.S. I do have a t2.8, with licence. Am I now free to copy it
to other machines?
∂20-Oct-86 0417 @MC.LCS.MIT.EDU:ramsdell%faron@mitre-bedford.ARPA Re: Public Domain
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Organization: The MITRE Corp., Bedford, MA
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Date: Mon, 20 Oct 86 07:06:48 edt
From: John D. Ramsdell <ramsdell%faron@mitre-bedford.ARPA>
Posted-Date: Mon, 20 Oct 86 07:06:48 edt
Message-Id: <8610201106.AA07286@faron.MENET>
To: jeff%aiva.edinburgh.ac.uk@Cs.Ucl.AC.UK, scheme@mc.lcs.mit.edu
Subject: Re: Public Domain
The best way to find out the status of the
T project is to write to one of the following address:
t-project@yale.ARPA
decvax!yale!t-poject.UUCP
tproj@YALECS.BITNET
John
∂20-Oct-86 1205 @MC.LCS.MIT.EDU:mhwu%hplmhw@hplabs.HP.COM [harris@hplwhh: Re: [ramsdell%faron@mitre-bedford.ARPA: Object-Oriented Schemes]]
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Date: Mon, 20 Oct 86 10:55:43 pdt
From: Henry M. Wu <mhwu%hplmhw@hplabs.HP.COM>
Message-Id: <8610201755.AA00122@hplmhw>
To: scheme@mit-mc
Subject: [harris@hplwhh: Re: [ramsdell%faron@mitre-bedford.ARPA: Object-Oriented Schemes]]
From: Warren Harris <harris@hplabs>
Date: Wed, 15 Oct 86 16:56:50 PDT
Subject: Re: [ramsdell%faron@mitre-bedford.ARPA: Object-Oriented Schemes]
To: mhwu@hplabs
In-Reply-To: Your message of 15-Oct-86 13:34:39
X-Mailer: NMail [$Revision: 2.6 $]
Henry:
Please forward my interest in object-oriented extensions to scheme.
I am familiar with scoops and have a paper describing the system's many
shortcommings.
Warren Harris
-------
∂27-Oct-86 1824 @MC.LCS.MIT.EDU:brooks%home%ti-csl.csnet@CSNET-RELAY.ARPA Multiple Values: A Survey
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Date: Mon, 27 Oct 86 16:08:57 cst
From: Gary Brooks <brooks%home%ti-csl.csnet@CSNET-RELAY.ARPA>
Message-Id: <8610272208.AA29154@>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: Multiple Values: A Survey
Multiple Values: A Survey
--------------------------
The current proposal (from Will's lunch minutes) for multiple return
values consists of the two functions:
(receive-values <fcn> <mv-thunk>)
which applies <fcn> to the multiple values returned by <mv-thunk>. And:
(return <v1> ... <vN>) or
(values <v1> ... <vN>)
which returns the values <v1> ... <vN>.
Also, in the semantics there is an auxiliary function single, which
currently raises an error if multiple values are returned. Question (3)
deals with issue of making the auxiliary function available in the
language and questions (7) and (10) indirectly deal with the semantics
for single.
1) Syntactic questions:
1a) What argument order do we want for receive-values?
1b) Do we want to use a different name for receive-values? Eg.
Multiple-value-call, multiple-value-apply, or something else?
1c) What name do we want for the multiple value return construct?
Return, values, something else?
2) Do we want receive-values and return to be essential or
non-essential?
3) Do we want to incorporate the auxiliary semantic function single
into the language (see also (6b)) as:
(single <mv-thunk>)
such that
(single (lambda () (return <v1> ... <vN>))) => <v1>.
Should it be essential or non-essential?
4) Should receive-values allow multiple multiple-value-thunks in a manner
similar to Common Lisp's multiple-value-call? That is all the values
from the various multiple-value-thunks would be "concatenated" before
being passed to the function.
5) Interaction with call-with-current-continuation. How are multiple
values returned from a continuation? Presumably,
(call/cc
(lambda (cont)
...
(cont (return <v1> ... <vN>))))
does not work since the (return <v1> ... <vn>) is in argument position.
Furthermore, I presume that
(call/cc
(lambda (k)
(receive-values
k
(lambda () (return <v1> ... <vN>)))))
won't work, since the escape procedure generated by call/cc is a
"function" of one argument, which would make the above application of
receive-values analogous to:
(receive-values (lambda (x) ...)
(lambda () (return <v1> ... <vN>)))
which (presumably) is an error.
5a) Modify continuations to take a variable number of arguments that
are returned as the multiple values of the continuation. Eg.
(k <v1> ... <vN>)
5b) Add a new procedure called
call-with-multiple-values-current-continuation (or call/mv/cc for short)
that takes a function of one argument, a multiple value escape
procedure. The escape procedure takes a thunk as an argument and
transmits the values returned by the thunk. Eg.
(call/mv/cc
(lambda (k)
(k (lambda () (return <v1> ... <vN>)))))
5c) Somehow modify the existing version of call/cc so that when the
escape procedure k is invoked, (k v) returns v and
(receive-values k (lambda () (return <v1> .. <vN>)
returns <v1> ... <vn>.
5d) Somehow modify multiple values so that they can be cohesively
returned in argument position. I.e. so (cont (return <v1> ... <vN>)
would work. (See Opinion message.)
5e) Something else?
6) What forms pass multiple values through?
More likely than not the following (relatively) tail recursive forms
pass back multiple values.
6a) Do LAMBDA, LET and LETREC pass back multiple values from their
bodies?
6b) Do IF, COND and CASE pass back multiple values from the arms of
the conditional?
6c) Does explicit and implicit BEGIN blocks pass back multiple values
from the last form in the block?
But what about other forms?
6d) Does DO pass back multiple values from the last form in the exit
clauses?
6e) Do AND and OR pass back multiple values from the last form? Or
in OR's case from any form?
6f) Can FORCE return multiple values? (If so how is DELAY
implemented (i.e. how is make-promise written))
6g) What other forms pass back multiple values?
6h) Are there any forms that never pass back multiple values?
7) What happens when multiple values are returned to a context which
doesn't expect them as in predicate position within a conditional or
argument position within an application. For example:
(if (return v1 ... VN)
<then>
<else>)
or
(f (return v1 ... VN) ...)
7a) Coerce the multiple values to a single value as in Common Lisp.
7b) Instantiate a (first class) multiple values object (see Opinion
message)
7c) It would be an error.
7d) An error would be signaled.
7e) Other?
8) Do we want to augment existing binding forms (let, let* letrec) to
destructure multiple values or introduce a multiple value version for
each binding form, or not include such a capability? In each of the
following examples, b1 would be bound to <v1> ... and bN to VN. Which
is preferred?
8a) (let (((b1 ... bN) ;; i.e. ((ids*) <exp>)
(return <v1> ... <vN>))
<other-bindings>)
<body>)
or (perhaps)
8b) (multiple-value-let or (8c) (multiple-value-let
(b1 ... bN) (((b1 ... bN)
(return <v1> ... <vN>) (return <v1> ... <vN>))
<body>) <other-bindings>)
<body>)
or
8d) other
Should (a)-(d) (if any) be essential or non-essential?
9) Similarly, do we want to augment set! and define to accept multiple
values, define new versions of these constructs or not include these
constructs? (In the case of define, augmentation would be incompatible
with the non essential forms of define.) Do we want to make this
essential or non-essential syntax? In the case of set!, which of the
following is preferred?
9a) (set! (id1 ... idN) (return <v1> ... <vN>))
And (b) or (c) for define.
or
9b) (multiple-value-set! (id1 ... idN) (return <v1> ... <vN>))
(multiple-value-define (id1 ... idN) (return <v1> ... <vN>))
or
9c) (multiple-value-set! id1 ... idN (return <v1> ... <vN>))
(multiple-value-define id1 ... idN (return <v1> ... <vN>))
or
9d) other
10) For those constructs that expect multiple values (presumably,
receive-values, multiple-value-let, multiple-value-let*,
multiple-value-letrec, and multiple-value-set!) what happens when too
few or too many values are returned. For example in:
(multiple-value-let
(((Id1 ... IdM) (return <v1> ... <vN>)))
<body>)
M arguments are expected and N arguments are returned.
10a) N > M More values returned than expected.
1) Ignore extra values.
2) It is an error.
3) An error is signaled.
4) other.
10b) M > N More values expected than returned.
1) Return as many as needed additional default values.
2) It is an error.
3) An error is signaled.
4) other.
11) What (if any) other constructs do we want for returning multiple
values? What should their names be? Do we want a thunk or an
expression for the multiple values form (see (6c)). Should these
constructs be essential or non-essential?
11a) the equivalent of (receive-values (lambda x x) <mv-form>)
1) (multiple-value-list <mv-thunk>) or
2) (values->list <mv-thunk>) or
3) none
4) other
11b) The equivalent of (apply values <list>)
1) (values-list <list>)
2) (list->values <list>)
3) none
4) other
11c) The equivalent of
(receive-values (lambda x (list->vector x)) <mv-form>)
1) (multiple-value-vector <mv-thunk>) or
2) (values->vector <mv-thunk>) or
3) none
4) other
11d) The equivalent of (apply values (vector->list <vector>))
1) (values-vector <vector>)
2) (vector->values <vector>)
3) none
4) other
11e) Any others?
∂27-Oct-86 1859 @MC.LCS.MIT.EDU:brooks%home%ti-csl.csnet@CSNET-RELAY.ARPA Multiple Values
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Date: Mon, 27 Oct 86 16:08:22 cst
From: Gary Brooks <brooks%home%ti-csl.csnet@CSNET-RELAY.ARPA>
Message-Id: <8610272208.AA29149@>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: Multiple Values
I'd like to see a consensus emerge on multiple values. To that end I
have summarized the existing proposal and questions from Will's lunch
minutes and added a number of other questions and issues. As the text
of these questions and issues is somewhat long (280 lines) I have
submitted it in a separate message entitled "Multiple Values: A Survey".
Also, since my own responses to the survey depend on a particular view
of multiple values, I have submitted yet another message explaining my
views on these issues and my response to the survey. The latter message
is entitled "Multiple values: An Opinion". Enjoy!
-- brooks
∂27-Oct-86 2205 @MC.LCS.MIT.EDU:brooks%home%ti-csl.csnet@CSNET-RELAY.ARPA Multiple Values: An Opinion
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Date: Mon, 27 Oct 86 16:09:35 cst
From: Gary Brooks <brooks%home%ti-csl.csnet@CSNET-RELAY.ARPA>
Message-Id: <8610272209.AA29167@>
To: rrrs-authors@MC.LCS.MIT.EDU
Subject: Multiple Values: An Opinion
Multiple Values: An Opinion
----------------------------
Values Objects
--------------
My view on multiple values is based on the principle that everything in
the language should be first class. For multiple values I postulate an
*IMMUTABLE* values object type. Values objects are created by the
values function. So,
(values <v0> ... <vN>)
creates a values object with values <v0> ... <vN>. Since values
objects are first class objects it would makes sense to bind a values
object to a (single) variable or cons up multiple value objects in a
list.
Components of a values object can be explicitly extracted with the
values-ref function. Like vectors, values object indexing is 0-based:
So,
(values-ref (values <v0> ... <vI> ... <vN>) I) ==> <vI>
Note that the function single can be simply defined as:
(lambda (vals) (values-ref vals 0))
The number of values in a values object can be computed with the
function values-length. Eg.
(values-length (values <v0> ... <vN>)) ==> N+1
Lastly, values objects can be identified by the predicate values?.
Values Objects and Identity
---------------------------
Since values objects are immutable they are intentionally
(operationally) identical (eqv?) if they have the same number of values
and if all the values are intentionally identical. Thus,
(eqv? (values <x1> <x2>) (values <y1> <y2>)) ==> #T
iff (eqv? <x1> <y1>) ==> #T and
(eqv? <x2> <y2>) ==> #T
Because of their immutability, The extensional identity (eq?-ness) of
multiple values is left unspecified. The contention here is that asking
the eq?-ness of values objects is uninteresting (maybe even
meaningless). It would be analogous to asking whether two bignums are
eq?.
Returning Values Objects
------------------------
A Values object is returned (directly or indirectly through a
continuation) just like any other type of object is returned.
Applying Functions to Values Objects
------------------------------------
Multiple-value-call takes a function and an expression which evaluates
to a values object and applies the function to the values in the values
object.
(multiple-value-call (lambda (x y) (+ x y)) (values 1 2)) => 3
Also, LAMBDA is augmented so that a lambda expression with a single
(unparenthesized) formal parameter (eg. (lambda x x)) is applied via
multiple-value-call, the formal parameter is bound to a values object of
all the actual parameters (Note BVL). Thus,
(multiple-value-call (lambda x x) (values 1 2)) <=> (values 1 2)
(Note: In (apply (lambda x x) ...), x would get bound to a list,
while in (multiple-value-call (lambda x x) ...), x would get bound to a
values object. I'm not enthused about the overloading of the single
unparenthesized bvl variable, but could not think of better syntax.)
Summary
-------
First class multiple values, values objects, are desirable for several
reasons:
1) It simplifies specifying which forms pass multiple values
through. Simply put, multiple values are passed through any form just
like any other values.
2) It simplifies from where multiple values can be returned. They can
be returned from anywhere. In contrast, in Common Lisp multiple values
can only be returned from the last form in an OR expression. In this
scheme multiple values can be returned from any form in an OR
expression.
3) In contrast to the original, thunkified proposal, the forms that
expect multiple values (multiple-value-call, single, etc.) could be
redefined such that the cumbersome multiple value thunks are replaced
with a simpler multiple value expression.
Eg. (single (lambda () (mvs ...))) => (single (mvs ...))
4) It simplifies the interaction with call/cc. To return multiple
values from a continuation just incant (cont (values <v0> ... <vN>)).
5) It allows programmers to manipulate multiple values without having
to inefficiently and unaesthetically coerce them to and from list structures.
Consider:
Expression oriented as opposed to thunk oriented.
(set! l (set! l
(cons (mvs ...) ...)) (cons
(multiple-value-call
list
(lambda () (mvs ...))
...)))
(multiple-value-call f (car l)) (apply f (car l))
Efficiency considerations
-------------------------
The immutability of values objects allows the compiler in cohoots with
the runtime system much latitude in representing multiple values. A
compiler/runtime strategy could be to return multiple values spread out
on the stack or in registers. When multiple values are returned to a
context which expects them the corresponding values object would never
have to be reified. For example, in
(define mvs (lambda (a b c) (values a b c)))
(multiple-value-let
(((x y z) (mvs 1 2 3)))
...)
a values object would not be allocated. Value objects would only have
to be allocated in the heap when multiple values are returned to a
context which is not expecting multiple values. For example,
(cons (values <v0> ... <vN> ) ...)
would require a values object to be allocated. However, a smart
compiler could avoid allocating a values object in many situations where
multiple values are indirectly expected. For instance, if the
equivalent of Common Lisp's (multiple-value-prog1 <exp1>... <expN>) was
implemented as:
(let ((x <exp1>))
<exp2>
...
<expN>
(multiple-value-call values x))
a smart compiler could avoid the allocation of the multiple values bound
to x by:
1) Leaving the multiple values returned by <exp1> spread out on the
stack.
2) Evaluating <exp2> through <expN>.
3) returning the spread out values of <exp1>.
Similar optimizations could be applied to multiple values returned by
know continuations, like cont, in:
(call/cc
(lambda (cont)
...
(cont (values <v0> ... <vN>))
...))
where the presence of the return in argument position would normally
require a values object to be allocated.
In even more esoteric situations, the compiler could represent (a
single group of) multiple values in a values object as well as spread out
on the stack. For example, in
(let [[[x (mvs ...)]]]
; spread x out on the stack for
; fast access
(multiple-value-call frob x) ; use the spread out values
(foo x) ; use the values object bound to x
(multiple-value-call frob x) ; use the spread out values, since
; we don't have to worry about
; foo side-effecting the values
; in x.
...)
My Answers to the Survey
------------------------
1) (a & b) (multiple-value-call <f> <mv-expression>)
(c) (values <v0> ... <vN)
2) Make multiple-value-call and values essential.
3) Include single as (single <mv-expression>) and make it non-essential.
4) Don't allow multiple multiple-value expressions in
multiple-value-call.
5) call/cc is not a problem with first class values objects.
6) Multiple values (i.e. values objects) are passed through forms just
like any other value is.
7) Just return a (first class) values object.
8, 9 & 10) Include:
(multiple-value-let (((ids*) form)*) <body>),
(multiple-value-let* (((ids*) form)*) <body>),
(multiple-value-letrec (((ids*) form)*) <body>) (maybe),
(multiple-value-set! (ids*) <form>), and
(multiple-value-define (ids*) <form>)
(maybe with mv-* nicknames) as non-essential. In any of the constructs
signal an error if too many or too few values are returned.
11) a) Include (values->list <mv-expression>) as non-essential.
b) Include (list->values <list>) as non-essential.
c) Include (values->vector <mv-expression>) as non-essential.
d) Include (vector->values <vector>) as non-essential.
e) other
include (values-ref <values-object> <index>) as essential
(values? <object>) as essential
∂28-Oct-86 0556 @MC.LCS.MIT.EDU:ramsdell%faron@mitre-bedford.ARPA Multiple values
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Date: Tue, 28 Oct 86 08:49:57 est
From: John D. Ramsdell <ramsdell%faron@mitre-bedford.ARPA>
Posted-Date: Tue, 28 Oct 86 08:49:57 est
Message-Id: <8610281349.AA21551@faron.MENET>
To: rrrs-authors%mc.lcs.mit.edu@mitre-bedford.ARPA
Subject: Multiple values
Cc: ramsdell@mitre-bedford.ARPA
I do not see any need for anything other than
some thing like the T version of multiple values.
That is RECEIVE-VALUES, RETURN (possibly called
VALUES), and the macro RECEIVE.
It would be nice if escape procedures can be applied
to a variable number of arguments, so that the following
would work:
(receive-values
(lambda (x y) (list x y))
(call-with-current-continuation
(lambda (k) (k 1 2)))) => (1 2).
but given how often call-with-current-continuation is
used, I think we should be content to pass back list
structure in those rare cases.
I strongly object to Gary Brook's proposal for multiple
values. The idea of adding a new data structure
smacks of a case of reading the semantic specification
of Scheme too literally. Using sequences as arguments
to expression continuations is a trick to get around
the fact that functions only take one argument in the
lambda calculus. The T experience shows that trick
is not needed in real implementations.
The most serious objection I have to Gary Brook's
proposal was the design philosophy that is implicit
in the proposal. There seemed to be no attempt to
explain why his proposal had any merit over the much
simpler version as proposed by Will Clinger. Any proposal
to solve one single language problem with a large addition of
functions and macros must be accompanied by an explanation.
While such proposals may be the norm in the Common Lisp
community, we must all remember that the Scheme report
starts its introduction with the words "Programming languages
should be designed not by piling feature on top of feature,
but by removing the weaknesses and restrictions that make
additional features appear necessary."
John
∂28-Oct-86 0615 @MC.LCS.MIT.EDU:jinx@GENEVA.AI.MIT.EDU Multiple values
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Date: Tue, 28 Oct 86 09:13:52 est
From: jinx@GENEVA.AI.MIT.EDU (Guillermo J. Rozas)
Message-Id: <8610281413.AA14222@geneva>
To: ramsdell%faron%mitre-bedford.ARPA@mc
Cc: rrrs-authors@mc.lcs.mit.edu
In-Reply-To: John D. Ramsdell's message of Tue, 28 Oct 86 08:49:57 est
Subject: Multiple values
I agree completely! All the extra mechanism proposed seems
unnecessary.
A single comments though,
What is the problem with having continuations expect multiple
arguments when they in fact are capable of returning them?
It seems to me that, it is not only the case that it would be nice if
(receive-values
(lambda (x y) (list x y))
(call-with-current-continuation
(lambda (k) (k 1 2)))) => (1 2).
worked, but instead it SHOULD work. Certainly the simplest
implementation of the whole mechanism that I can think of would take
care of this.
∂28-Oct-86 1358 @MC.LCS.MIT.EDU:andy@hobbes.ARPA Re: Multiple values
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Date: Tue, 28 Oct 86 13:48:40 PST
From: andy@hobbes.ARPA (Andy Cromarty)
To: rrrs-authors@mc.lcs.mit.edu
Subject: Re: Multiple values
If multiple values are to be defined for Scheme, I personally
would prefer that
(a) They be assigned inessential status, and
(b) Some comment be made in the R?RS admonishing implementors to
attempt to make lists be of roughly equivalent efficiency, or
suggesting some stylistic conventions for MV use.
The latter suggestion is motivated by frequent observation of
what seem to me to be excessive or abusive instances of MV use in
practical code written in other LISPs.
Returning both the number-theoretic quotient and the remainder
from a division routine seems like a use of MV's about which
few people would complain; but using MV's instead of creating
and passing composite data structures for related values that are
meant to be treated as an abstract object seems an unnecessary and
obfuscatory use of MV's. Often it seems people use MV's in such
cases either out of lack of aesthetic sense or because consing up
a data structure is too costly. An admonition to programmers could
address the former problem; and admonition to implementors, the latter.
asc
∂30-Oct-86 0139 @MC.LCS.MIT.EDU:harris%hplwhh@HPLABS.HP.COM Re: Multiple Values: An Opinion
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From: Warren Harris <harris%hplwhh@HPLABS.HP.COM>
Message-Id: <8610281933.AA05914@hplwhh>
Date: Tue, 28 Oct 86 11:33:30 PDT
Subject: Re: Multiple Values: An Opinion
To: brooks%home%ti-csl.csnet%csnet-relay.arpa@CSNET-RELAY.ARPA,
rrrs-authors%MC.LCS.MIT.EDU%csnet-relay.arpa@CSNET-RELAY.ARPA
In-Reply-To: Your message of 27-Oct-86 16:09:35
X-Mailer: NMail [$Revision: 2.6 $]
I'm sorry, I know I'm not supposed to be on this line, but I just had
to state my opinion of multiple values. I think this is one (!) of the
most poorly thought out (and most haphazardly integrated) concepts in
common lisp. I'd hate to see scheme suffer from the same disease.
First of all, I see no need for the construct whatsoever. Each of
the functions to deal with multiple values can be replaced by existing
scheme functions:
(values <v1> ... <vn>) => (list <v1> ... <vn>)
(receive-values <fn> <mv-thunk-or-1st-class-mv-obj>) => (apply <fn> <list>)
(single <mv-thunk-or-1st-class-mv-obj>) => (car <list>)
(multiple-value-set! (<id1> ... <idn>) <mvs>) =>
(map set! '(<id1> ... <idn>) <list>)
Therefore, the multiple value constructs add no new functionality to the
language (shame). They are simply included to increase lisp's efficiency
(a job which is best left up to the compiler). In light of todays cdr-coded
lists I would think consing can be accomplished as efficiently as vector
allocation for multiple-value objects. I would assume the same tricks could
be employed for register or stack allocation of some lists, as they are
returned to functions which immediately destructure them.
All of your efficiency considerations still hold:
Efficiency considerations
-------------------------
A compiler/runtime strategy could be to return lists spread out on the
stack or in registers. When lists are returned to a context which
expects them the corresponding list object would never have to be
reified. For example, in
(define mvs (lambda (a b c) (list a b c)))
(let* ((m (mvs 1 2 3))
(x (first m))
(y (second m))
(z (third m)))
...)
a list object would not be allocated. List objects would only
have to be allocated in the heap when lists are returned to a context
which is not expecting a list. For example,
(cons (list <v0> ... <vN> ) ...)
would require a list object to be allocated. However, a smart
compiler could avoid allocating a list object in many situations where
lists are indirectly expected. For instance, if the equivalent of
Common Lisp's (multiple-value-prog1 <exp1>... <expN>) was implemented
as:
(let ((x <exp1>))
<exp2>
...
<expN>
x)
a smart compiler could avoid the allocation of the list bound
to x by:
1) Leaving the list returned by <exp1> spread out on the
stack.
2) Evaluating <exp2> through <expN>.
3) returning the spread out list of <exp1>.
Similar optimizations could be applied to lists returned by
know continuations, like cont, in:
(call/cc
(lambda (cont)
...
(cont (list <v0> ... <vN>))
...))
where the presence of the list in argument position would normally
require a list object to be allocated.
-----
Lets work at optimizing the compiler, not giving the programmer
his own hooks to optimize. I think most people avoid multiple values
anyway.
Warren Harris
HP Labs, bld 3U
1501 Page Mill Rd.
Palo Alto, CA 94040
harris%hplwhh@hplabs.HP.COM
P.S. How about a nice destructuring facility similar to multiple-value-bind
except for lists (like zetalisp's destructuring-bind). For example, what
could be implemented with multiple values as:
(defun foo (x y z) (values x y z))
(multiple-value-bind (x y z) (foo 1 2 3))
or regular lists as:
(defun foo (x y z) (list x y z))
(let* ((all (foo 1 2 3))
(x (first all))
(y (second all))
(z (third all)))
...)
could be more concisely stated as:
(destructure (x y z) (foo 1 2 3)
...)
Also, arbitrary trees could be destructured:
(destructure ((x . y) z) '((a b c d) e)
(print y))
=> (b c d)
This would help the compiler in its optimization, as well as give the
programmer a succinct syntax for a routine procedure.
-------
∂30-Oct-86 1228 @MC.LCS.MIT.EDU:adams%tekchips.tek.csnet@CSNET-RELAY.ARPA multiple values
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Date: Wed, 29 Oct 86 12:28:59 PST
From: Norman Adams <adams%tekchips.tek.csnet@CSNET-RELAY.ARPA>
Message-Id: <8610292028.AA08573@tekchips.TEK>
Subject: multiple values
To: rrrs-authors@MC.LCS.MIT.EDU
The language syntax and procedure library both favor calling with multiple
arguments over returning multiple values (no surprise considering that we
haven't have multiple return values in the language).
I seems to me easier to fix the procedure library than the syntax.
(Anyone want to adopt the "{...}n" notation that Steele mentions
in "The Ultimate Declarative"?)
Gary's survey identifies some rough edges that adding multiple values
causes. I favor:
a) changing call-with-current-continuation as described in 5a
(call/cc creates n-ary procedures that invoke the continuation with as
many arguments)
b) using RECEIVE (or the equivalent), instead of the alternatives of
either hacking up all the binding forms, or adding a bunch of
new binding forms.
c) living with it until we have more experience.
I'm for no coersions, no multiple-value-call.
-Norman
-------
∂30-Oct-86 1339 @MC.LCS.MIT.EDU:jinx%geneva.ai.mit.edu@CSNET-RELAY.ARPA Multiple Values: An Opinion
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From: "Guillermo J. Rozas" <jinx%geneva.ai.mit.edu@CSNET-RELAY.ARPA>
Message-Id: <8610301542.AA17018@geneva>
To: harris%hplwhh@HPLABS.HP.COM
Cc: brooks%home%ti-csl.csnet%csnet-relay.arpa%csnet-relay.arpa@CSNET-RELAY.ARPA,
rrrs-authors%MC.LCS.MIT.EDU%csnet-relay.arpa%csnet-relay.arpa@CSNET-RELAY.ARPA
In-Reply-To: Warren Harris's message of Tue, 28 Oct 86 11:33:30 PDT
Subject: Multiple Values: An Opinion
I'm sorry, I know I'm not supposed to be on this line, but I just had
to state my opinion of multiple values. I think this is one (!) of the
most poorly thought out (and most haphazardly integrated) concepts in
common lisp. I'd hate to see scheme suffer from the same disease.
I can understand your objections when you look at the CL book and
examine the rules for when multiple values are passed back and not.
On closer inspection, however, you will notice that the rule is
uniform (although specified in utmost detail): When dealing with a
compound expression, multiple values are passed back from the
subexpression into which the evaluation of the compound expression
reduces. In other words, tail-recursion is what determines when
multiple values are passed back. Unfortunately CL does not require
its implementations to be properly tail-recursive, so they could not
explain the semantics of multiple values in terms of tail-recursion.
We don't have this problem, so the behaviour can be described simply,
and the huge case list can be added as examples, not as the definition
of the bahaviour.
Agreed that there is no semantic need for multiple values, and that
the main consideration is efficiency, but there is no reason not to
add them to the language with inessential status, as long as we also
specify that implementations are free to make them be the obvious
procedures which work on lists, or even the suggestion below (which I
prefer).
I don't agree with you on one count however. Most of the compiler
optimizations that I see proposed very often suffer from a few bad bugs:
- The idea is simple, so it is assumed that the implementation is also
simple. This is obviously a fallacy. I'm specially wary of
optimizations that require a great deal of analysis. I'm not saying
it cannot be done, just that it is often the case that it takes a
great deal more work than anticipated.
- The optimizations break down across module boundaries. The main
problem with static analysis is that it needs a closed world model.
This is often hard to provide, and even inappropriate in an
interactive development environment.
- Static optimizations to improve performance badly hurt interpreters.
I know the MIT crowd is in the minority here, but we believe in
interpreters as our main development tool. Although we also want high
performance compilers, we don't want to sacrifice any performance in
the interpreter.
Consider the following proposal instead, which does not require much
(if any) compiler overhead:
(define (receive-values fn th)
((th) fn))
(define (values . all)
(lambda (receiver)
(apply receiver all)))
Note that a compiler which understands a little about tail arguments
can optimize the above relatively easily, given that the construction
and destructuring of the list is purely local and contained inside
VALUES. Even further, since the whole mechanism is contained in 2
procedures, they can easily be implemented as primitives, with
whatever efficiency is desired. Static compiler analysis to reduce
consing can still be used, but this time it is closure analysis of the
sort many Scheme compilers already do.
Note that the above proposal implies that intermediate forms in AND,
OR, and possibly other special forms would have to be treated
specially, since there is a difference between returning a "normal"
value, and explicitely returning 1 value.
PS: There are two other objections to your message, both minor:
- SET! is a the keyword of a special form, thus it cannot be mapped.
- I (and a fair amount of other people) do not believe in cdr-coding.
It is clearly expensive on stock hardware, and it is not clear to me
that it is not expensive on special purpose hardware, besides adding
unnecessary hair to the complete system and in particular the garbage
collector, and we all know where this leads.
∂30-Oct-86 1520 @MC.LCS.MIT.EDU:ANDY@Sushi.Stanford.EDU Re: multiple values
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Date: Thu 30 Oct 86 12:25:22-PST
From: Andy Freeman <ANDY@Sushi.Stanford.EDU>
Subject: Re: multiple values
To: rrrs-authors@MC.LCS.MIT.EDU
In-Reply-To: <8610292028.AA08573@tekchips.TEK>
Message-ID: <12250998624.20.ANDY@Sushi.Stanford.EDU>
I'd like to bring up another multiple-value proposal but first I
have a question. Why is the scheme community attempting to
standardize this now? Is it really that well understood?
This proposal is a variant on the technique Carolyn Talcott used
in her thesis; Richard Weyrauch was also involved in that work.
Their idea requires one procedure; I'll call it values. Procedure
invocation spreads multiple values; (cons (values 1 2)) is completely
equivalent to (cons 1 2) and (list (values) 4 (values 1 2) 3) is
equivalent to (list 4 1 2 3). (It should be obvious that (values 1)
is completely equivalent to (values (values 1)).) In Talcott's
system, the last variable in a lambda expression's formal argument
list is preceded by an implicit period; I feel that the optional
explicit period of r↑3rs' syntax is superior.
Call/cc is generalized appropriately as well. If I understand
receive-values correctly, it is the same as apply.
Most of the other proposals strike me an attempt to add yet another
aggregate data type (in addition to lists and vectors) that predefined
procedures will use to return a number of values. This is not a bad
idea, different implementations can use different representations, yet
the coercion rules and additional procedures (if a form returns
multiple values, all but the first are discarded unless the programmer
has mastered subtle rules involving tokens not unlike funcall and #')
bother me.
Talcott's scheme is succinct and builds on the rest of the language.
(Look how much of this message was used to explain the idea.) Its
only disadvantage is that you can't tell how many arguments are being
passed by counting s-expressions.
-andy
-------
∂30-Oct-86 2204 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU multiple values
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Date: Thu, 30 Oct 86 22:08:03 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: multiple values
To: rrrs-authors@MC.LCS.MIT.EDU, klotz@OZ.AI.MIT.EDU
In-reply-to: Msg of Mon 27 Oct 86 16:08:57 cst from Gary Brooks <brooks%home%ti-csl.csnet at CSNET-RELAY.ARPA>
Message-ID: <[AI.AI.MIT.EDU].112644.861030.JAR>
Since I'm the one who added the procedures VALUES (a.k.a. RETURN) and
RECEIVE to T, it seems appropriate that I should say a word or two about
what the heck I had in mind when I did so.
In the T implementation, the low-level protocols for call to unknown
procedure and return to unknown continuation are almost identical. The
compiler does CPS conversion and doesn't see the difference much, and
the data representation for implicit continuations is the same as that
for procedures.
The implementation symmetry suggested that maybe some surface-language
symmetry was worth experimenting with. This was corroborated by the
frequent need for some way to return more than one result value to the
caller. I had been doing the latter with
(foo arg1 arg2 ... argn (lambda (val1 val2 ... valm) body)),
and this syntax seemed pretty unweildy (it doesn't indent nicely, for
example); using lists and destructuring wasn't much better. So in T2,
anticipating future compiler support in T3, a procedure VALUES was
defined to be more or less the same as LIST (actually closer to VECTOR
-- the details are irrelevant), and a macro RECEIVE was invented to get
result values:
(receive (val1 val2 ... valm)
(foo arg1 arg2 ... argn)
body)
== (apply (lambda (val1 val2 ... valn) body)
(foo arg1 arg2 ... argn))
The beauty of VALUES and RECEIVE is that they're totally noncommittal
about implementation. The above is a correct implementation of the
abstraction, but so is the T3 implementation, where
(define (values . vals)
(c-w-c-c (lambda (k) (apply k vals))))
and
(receive (val1 val2 ... valm)
(foo arg1 arg2 ... argn)
body)
== (receive-values (lambda () (foo arg1 arg2 ... argn))
(lambda (val1 val2 ... valm) body))
[maybe I have the argument order reversed, I alwasy forget]
and RECEIVE-VALUES is a new primitive procedure. (We'd never expect a
user to invoke RECEIVE-VALUES explicitly, but it has to exist so that
RECEIVE can be a macro rather than a special form. It would be
necessary in Scheme to exactly the same extent that MAKE-DELAY is
necessary, which is somewhat.)
Thus if T programs have to ported to some other Scheme dialect, or if T
decides at some future point that multiple-value-returns are a horrible
idea and should be retracted, all our code will still work because the
abstraction is noncommittal. The nice thing is simply the notation, not
the implementation. The fact that T3 implements it well encourages its
use (and makes GC's less frequent, which, unfortunately, is a concern),
but is incidental.
A small benefit of having this facility be primitive is that you have an
opportunity for some error checking not previously available, namely you
can get wrong-number-of-return-value errors. This is good for the same
reason that wrong-number-of-argument errors are good. But note that it
is a necessary condition in order for the facility to permit varying
implementations.
(I don't see strong reasons for adding destructuring to LET or for any
other linguistic support for the multiple return values besides VALUES
and RECEIVE.)
I'm still not sure how I feel about the feature. Certainly the
abstraction is a good idea. As for the semantical foundations, I feel
pretty strongly that call and return should be symmetrical. If you can
have many arguments, you should be able to return many values. But note
that (P -> Q) does not necessarily imply Q, it might imply not P. My
opinion now is that it's probably better to achieve symmetry by flushing
multiple-argument procedures rather than by introducing multiple-value
returns, but this is incompatible with the present shape of Scheme, so I
won't recommend it for this audience.
Gary gives good reasons for introducing immutable data structures.
Algol 68 and ML have the right idea; Lisp and Scheme got it wrong. It
would certainly be worthwhile to experiment with immutable pairs,
strings, and vectors. Adding immutable objects onto Scheme (especially
one type without the others) might be a mistake, and it could be the
case that adding immutable objects as an afterthought like this,
coexisting with mutable objects, would result in a very inelegant
language. (Maybe it could result in a very elegant language... anyone
for ((immutably cons) x y)? I don't know.) But I think this is a
question independent of the multiple-value question, and Gary's proposal
is both more complicated and has more far-reaching consequences than
RECEIVE and VALUES, which are trivial.
I like the idea of adding RECEIVE and VALUES to Scheme *without
specifying what happens when some VALUES go somewhere other than to a
RECEIVE*. The mechanism can be added trivially to any Scheme, and those
that want to optimize it (or which already do) may feel free.
Minimalists can implement the mechanism with lists or closures, Gary can
implement it with immutable vectors, Schemes which are embedded in
Common Lisp or cohabit with it may use CL's multiple values, and T can
do what it does. It is minimal and noncommittal, it's a pleasant
notation, it captures a common pattern of usage, so why not.
- Jonathan
∂31-Oct-86 1840 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU multiple values
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Date: Fri, 31 Oct 86 21:41:46 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: multiple values
To: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Fri 31 Oct 86 03:23:10 EST from Alan Bawden <ALAN at AI.AI.MIT.EDU>
Message-ID: <[AI.AI.MIT.EDU].113058.861031.JAR>
Date: Fri, 31 Oct 86 03:23:10 EST
From: Alan Bawden <ALAN at AI.AI.MIT.EDU>
I don't use CL multiple values in any situation where LIST will
suffice. I use it just in case I want some "by-products" to be
transparently discarded by all but a few callers. This is why
multiple values were added to the Lisp Machine in the first place,
and its still the only reason I see to use it.
...
As Alan has tactfully pointed out to me, none of the multiple-value
features that Gary Brooks and Andy Freeman and I and others have been
talking about bear much resemblance to CL multiple values, and they are
really intended to solve a different problem. The terminology is a
problem here; we really shouldn't be saying that these constructs do
"multiple value returns" because Lisp Machine Lisp and its derivatives
(CL) have been using that term for quite a while to mean something quite
different. (I might have called the LM feature "extra value returns"...)
We should no more think that we're "cleaning up something CL
did wrong" than we should think that omitting optional or keyword arguments,
or macros or packages, solves the problems that those features
were introduced to address.
I agree that the RECEIVE/VALUEs feature is of marginal usefulness. I
don't think this is the most important outstanding issue we have to talk
about; macros, modules, opaque types, tables, and even bitwise logical
operators all loom larger. Of course, the more agreement we can get on
any feature at all, the better.
A suggestion on how to proceed: we needn't think of every discussion as
aiming towards something to be included in R↑4RS. If just 2
implementations agree on a way to do something, we have still gained
something. We should consider creating an auxiliary document, much more
informal and open-ended than a R↑nRS, describing possibilities for
standard libraries and utilities, possibly with multiple different ways
to do things if no agreement can be reached. Unanimity may be too
stringent a requirement if this group is to make much progress....
Jonathan
∂31-Oct-86 1916 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Journal of Lisp and Symbolic Computation -- call for papers
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Date: Fri, 31 Oct 86 22:11:09 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: Journal of Lisp and Symbolic Computation -- call for papers
To: scheme@MC.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].113067.861031.JAR>
Date: Fri, 31 Oct 86 12:34:05 PST
From: edsel!sunvalleymall!jlz at navajo.stanford.edu (Jan Zubkoff)
To: navajo!Common-lisp%sail at navajo.stanford.edu
cc: sunvalleymall!jlz at navajo.stanford.edu
Re: Call for Papers
Message-Id: <8610312034.AA09846@sunvalleymall.edsel.uucp>
LISP AND SYMBOLIC COMPUTATION:
An International Journal
10/27/86
CALL FOR PAPERS
LISP AND SYMBOLIC COMPUTATION: An International Journal (LASC) is
a new journal published by Kluwer Academic Publishers. Richard
P. Gabriel, Lucid, Inc. and Guy L. Steele Jr., Thinking Machines,
Inc. are Editors-in-Chief.
The aim of this new journal is to present a forum for current and
evolving symbolic computing, focusing on LISP and
object-oriented programming. The scope includes:
* Programming language notations for symbolic computing
(e.g., data abstraction, parallelism, lazy evaluation,
infinite data objects, self-reference, message-passing,
generic functions, inheritance, encapsulation,
protection, metaobjects).
* Implementations and techniques (e.g., specialized
architectures, compiler design, combinatory models,
garbage collection, storage management, performance
analysis, smalltalks, flavors, common loops, etc.).
* Programming logics (e.g., semantics and reasoning about
programs, types and type inference).
* Programming environments and tools (e.g.,
Knowledge-based programming tools, program
transformations, specifications, debugging tools).
* Applications and experience with symbolic computing
(e.g., real-time programming, artificial intelligence
tools, experience with LISP, object-oriented
programming, window systems, user interfaces, operating
systems, parallel/distributed computing.
!
REQUIREMENTS FOR SUBMISSION
Timetable. Authors must submit five (5) complete copies of their papers.
Notice of acceptance or rejection will be sent to the first author.
Appearance. Each copy of the paper should be clearly legible.
Papers should be printed on 8-1/2 by 11" paper, double spaced
with at least 1 inch margins with no smaller than 12 pt. type.
Title Page. Each copy of the paper must have a title page (separate from
the body of the paper) containing the title of the paper, the names and
addresses of all the authors. The affiliation appearing under the author's
name should be the name of the organization for which the work was carried
out. When this is no longer the author's current affiliation, the latter
is given in the address footnote on the first page. The title page must
specify one topic from the scopes listed on the reverse side of this page.
Abstract. The abstract should be 150 to 200 words and should be short and
direct. It should be informative enough to serve as a substitute for
reading the paper itself. Work planned but not done should not be
described in the abstract. Do not display formulas and do not use citation
reference numbers.
Review Criteria. Each paper will be reviewed by experts in the area
specified from the scope as the topic of the paper. Acceptance will be
based on overall merit and significance of the reported research, as well
as the quality of the presentation.
Please send papers to:
Jan Zubkoff
Associate Editor, LASC
Lucid, Inc.
707 Laurel Street
Menlo Park, CA 94025
edsel!jlz@su-navajo
(415) 329-8400
Suggestions and inquiries to:
Dick Gabriel Guy L. Steele Jr.
Editor-in-Chief Editor-in-Chief
Lucid, Inc. Thinking Machines, Inc.
707 Laurel Street 245 First Street
Menlo Park, CA 94025 Cambridge, MA 02142
rpg@sail gls@think.COM
(415) 329-8400 (617) 876-1111
∂03-Nov-86 0855 @MC.LCS.MIT.EDU:gls@Think.COM Marvel?
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Date: Mon, 3 Nov 86 11:24 EST
From: Guy Steele <gls@Think.COM>
Subject: Marvel?
To: ANDY@Sushi.Stanford.EDU, gjs@MC.LCS.MIT.EDU, rrrs-authors@mc.lcs.mit.edu
Cc: rpg@SU-AI.ARPA, gls@AQUINAS
In-Reply-To: <12251488191.9.ANDY@Sushi.Stanford.EDU>
Message-Id: <861103112403.4.GLS@POLYCARP.THINK.COM>
Date: Sat 1 Nov 86 09:14:39-PST
From: Andy Freeman <ANDY@Sushi.Stanford.EDU>
Apparently you wrote a language that had a multiple values
scheme much like the one I attributed to Talcott and Weyrauch.
Can you comment on it to rrrs-authors? (T&W like it and have
stayed with it; you abandoned it. I'm sure both had their
reasons.)
Yes. For a while I worked on a dialect of Scheme called MARVEL
(Multiple-Return-Value--Expression Lisp; if you ask "where does
the `A' come from?" I say "A is for Acronym").
It did pretty much all the obvious things: every function call was
implicitly like the Common Lisp MULTIPLE-VALUE-CALL, and most
side-effecting forms such as SETQ, PRINT, and COMMENT were made to
return zero values. I believe I also arranged for variables to
be able to hold multiple values.
My experience with the language was that it was perfectly clean
and elegant, but programs that made non-trivial use of multiple
values were very hard to read, precisely because of the loss
of the one-form/one-value correspondence. Having the extra power
everywhere in the language was not worth the loss of clarity.
I therefore abandoned the experiment without writing it up.
(Maybe I should have, but there were other, more promising variations
of Scheme to explore.)
I am cc'ing this message to Dick Gabriel, who worked with Weyrauch on
the implementation of SEUS, a language with this geneal flavor. I
recall him having reported to me the same results with their language,
but he should have the chance to speak for himself.
I believe that experience with the POP languages (especially POP-2)
may be relevant to ths discussion, but I am not an expert there.
--Guy
∂03-Nov-86 1221 @MC.LCS.MIT.EDU:RPG@SAIL.STANFORD.EDU gls@AQUINAS/cc
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Date: 03 Nov 86 1214 PST
From: Dick Gabriel <RPG@SAIL.STANFORD.EDU>
Subject: gls@AQUINAS/cc
To: ANDY@SUSHI.STANFORD.EDU, gjs@MC.LCS.MIT.EDU,
rrrs-authors@MC.LCS.MIT.EDU
Multiple Values
I wrote the SEUS compiler for the HP300 (?) version of SEUS. SEUS had
what-I-guess-are-now-called CARTs, which are coalescing multiple values.
Whenever 2 CARTs came near each other, they joined into one larger
one. This resulted in this code
(defun foo (x) (values x x x))
(defun bar (x)(values x x x x))
(list (foo 1)(bar 2)(foo 3))
doing this
=> (1 1 1 2 2 2 2 3 3 3)
The code, as Steele mentions, was elegant in a certain sense, but very
hard to read most of the time, because you had to take into account that
some other values than the primary value (the first one) would be passed
to some program. The places where SEUS code was easy to read were when you
were writing something that, in Common Lisp, would be
(multiple-value-call #'foo (baz)(bar))
The places where it was hard to read were when you were writing something
that, in Common Lisp, would be
(foo (baz) (bar))
That is, there was no easy way to check that the right values from the
right places got passed. I think that the latter is the more commonly
used case, so SEUS was optimized the wrong way.
It was hard to do this:
(defun foo (x)(values x (+ x 1) (+ x 2)))
(defun baz (x y) ...)
such that calling BAZ on (FOO 1) and (FOO 2) passed 1 and 2 to BAZ.
I recall that SEUS had no way to do this until I was half-way through
writing the compiler. I also recall that variables could be bound to
CARTs, somehow, as part of the solution to the problem - that is,
you could get X to be bound to the CART, [1 2 3], and Y to [2 3 4].
When the Common Lisp multiple value scheme was being devised, I thought
that we (the designers) should look at SEUS for its experience. I'm now
glad we didn't do anything more that invent MULTIPLE-VALUE-CALL as a
result of that experience.
-rpg-
∂05-Nov-86 0305 @MC.LCS.MIT.EDU:GOERZ@SUMEX-AIM.ARPA [Gunther Goerz <GOERZ@SUMEX-AIM.ARPA>: CScheme for 68K]
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Date: Wed 5 Nov 86 02:48:18-PST
From: Gunther Goerz <GOERZ@SUMEX-AIM.ARPA>
Subject: [Gunther Goerz <GOERZ@SUMEX-AIM.ARPA>: CScheme for 68K]
To: JAR@AI.AI.MIT.EDU, SCHEME@MC.LCS.MIT.EDU
Message-ID: <12252466434.15.GOERZ@SUMEX-AIM.ARPA>
Mail-From: GOERZ created at 24-Oct-86 03:24:44
Date: Fri 24 Oct 86 03:24:44-PDT
From: Gunther Goerz <GOERZ@SUMEX-AIM.ARPA>
Subject: CScheme for 68K
To: scheme%mit-mc.csnet@RELAY.CS.NET
cc: Goerz@SUMEX-AIM.ARPA
Message-ID: <12249316417.13.GOERZ@SUMEX-AIM.ARPA>
Patrick Greussay of the Univ of Paris 8 and LITP has implemented (at least
one version of) SCHEME in C which is running on a variety of machines,
including 68000 systems.
--Guenther
-------
-------
∂07-Nov-86 0351 @MC.LCS.MIT.EDU:enea!tut!jh@seismo.CSS.GOV eval and orbit
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Date: Fri, 7 Nov 86 13:20:28 -0200
From: enea!tut!jh@seismo.CSS.GOV (Juha Hein{nen)
Return-Path: <jh@tut>
Message-Id: <8611071120.AA033441@tut.uucp>
To: scheme@MC.LCS.MIT.EDU
Subject: eval and orbit
I asked to be put on this list a couple of weeks ago and haven't
received any postings. Here comes mine as a test.
1. What is the rational in omitting eval from Scheme?
My program is supposed to read values of enumerated types (i.e.
symbols) and then convert the symbols to their values. In regular
Lisp I would write (eval (read)) to get the value but how am I
supposed to do that in Scheme? Use a mapping function from names to
values or is there a simpler way?
2. Where can I get the Orbit Scheme compiler for my Sun-3
workstation?
Juha Heinanen
Tampere Univ. of Technology
Finland
∂07-Nov-86 1716 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Automatic removal from list...
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Date: Fri, 7 Nov 86 20:13:16 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: Automatic removal from list...
To: scheme@MC.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].115915.861107.JAR>
Scheme@MC is a big mailing list. On average, one or two members become
unreachable each week, due to changes in routing, gateways being down,
etc. Be warned that I will ruthlessly remove from the list any
recipients to whom mail is undeliverable. If you change your address,
be sure to send a note to Scheme-Request@MC. If your machine has been
down or off the net for a while (usually the various mail systems retry
for three to seven days), and mail bounces as a result, you will likely
be removed. This is the only way I'll be able to keep things under
control and prevent people who send messages to Scheme from being
deluged with enormous quantities of bounced mail. Just send me a
message when you're back on, or if you think one of your gateways could
have been down and you haven't seen a message for a couple of weeks.
I sure hope that one of these days electronic mail will be able to reach
people as reliably as physical mail does. The current state of the art
of e-mail is quite inferior in the respect, probably at about the same
point of development that physical mail was in about the 15th century.
Jonathan
∂07-Nov-86 1817 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU MIT AIM 848a
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Date: Fri, 7 Nov 86 20:51:52 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: MIT AIM 848a
To: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].115926.861107.JAR>
I'll mail copies to y'all (unless I don't have your address or you tell
me not to or you already have one).
Jonathan
∂07-Nov-86 1839 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Hot off the press...
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Date: Fri, 7 Nov 86 20:48:46 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: Hot off the press...
To: scheme@MC.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].115925.861107.JAR>
The new report is ready! Get them while they last!
It's available in a handsome red binding from the MIT AI Lab
publications office; the address is:
Elizabeth Heepe
Publications, Room NE43-818
MIT Artifical Intelligence Laboratory
545 Technology Square
Cambridge MA 02139
Ask for MIT Artificial Intelligence Memo 848a, the "Revised↑3 Report on
the Algorithmic Language Scheme". Enclose a check for $6.00 per copy
(U.S. funds) payable to the MIT Artificial Intelligence Laboratory.
Prepayment is required.
This version (dated September 1986) supersedes last summer's report,
which was AI memo 848 (this one is 848a). It also supersedes (but is
very similar to) the draft which was passed out at the Lisp and FP
Conference in August.
It is identical (same original) to the version that will be printed in
SIGPLAN this December, except that in the MIT AI memo version it
additionally includes a previously unpublished article by Abelson and
Sussman entitled "Computation: An Introduction to Engineering Design".
If you want to cite it, probably better to cite the SIGPLAN version
since that will be available to a wider audience:
Jonathan Rees and William Clinger, editors.
"Revised↑3 Report on the Algorthmic Language Scheme."
SIGPLAN Notices 21(12), September 1986.
The report will also appear as an Indiana University CSD Technical
Report.
Here is a brief summary of the more important differences between the
1985 and 1986 versions of the language:
- Added: delay, force, boolean?, procedure?
- Removed: #!null, rec, named-lambda, append!, object-hash,
object-unhash, 1+, -1+, some of the string operators,
"curried define"
- Redundant names removed: sequence, =?, <?, <=?, >?, >=?
- Renamed: #!true -> #t, #!false -> #f
- Changed: (define (foo ...) ...) now means
(define foo (lambda (...) ...)), not
(define foo (named-lambda (foo ...) ...))
Other, lesser, changes are enumerated in a special section on page 36.
- Jonathan Rees
∂08-Nov-86 1121 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU multiple
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Date: Sat, 8 Nov 86 14:23:05 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: multiple
To: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <[AI.AI.MIT.EDU].116160.861108.JAR>
I didn't mean for my message to squelch debate. Surely someone
disagrees with me. Speak up.
Jonathan
∂08-Nov-86 1303 @MC.LCS.MIT.EDU,@MIT-MULTICS.ARPA:REMARCK@UCLASSCF.BITNET This account is scheduled to be deleted soon...
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Date: Sat, 08 Nov 86 12:39:12 PST
From: REMARCK@UCLASSCF (Marc Kriguer)
To: scheme@MC.LCS.MIT.EDU
Subject: This account is scheduled to be deleted soon...
And to avoid the last-minute rush, I have to start dropping myself from
all the mailing lists I am on. Please remove my name from the
scheme mailing list.
Thank you very much!
Marc Kriguer
∂09-Nov-86 0851 @MC.LCS.MIT.EDU:JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU eval and orbit
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Date: 9 Nov 1986 11:45 EST (Sun)
Message-ID: <JINX.12253580092.BABYL@MIT-OZ>
From: Bill Rozas <JINX%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU>
To: enea!tut!jh@SEISMO.CSS.GOV (Juha Hein{nen)
Cc: scheme@MC.LCS.MIT.EDU
Subject: eval and orbit
In-reply-to: Msg of Fri 7 Nov 86 13:20:28 -0200 from enea!tut!jh at seismo.CSS.GOV (Juha Hein{nen)
My program is supposed to read values of enumerated types (i.e.
symbols) and then convert the symbols to their values. In regular
Lisp I would write (eval (read)) to get the value but how am I
supposed to do that in Scheme? Use a mapping function from names to
values or is there a simpler way?
Besides the fact that EVAL is not really necessary for most
programming, the problem is that we could not agree on what eval would
mean or do (we didn't try very hard because of the other reason):
Some implementations have a single global environment where
expressions could be evaluated. In these implementations (eval <x>)
would make sense.
Other implementations have multiple environments where code can be
evaluated. In these implementations (eval <x>) does not make much
sense. Eval needs to take a second argument specifying what
environment to evaluate in, and it is not clear that a reasonable
default can be provided so that 1 argument EVAL could work.
You should use a mapping function or something like it if you want
your code to be portable. Most implementations have an EVAL procedure
(with different behavior) which you can use if you don't care about
that.
∂10-Nov-86 1301 @MC.LCS.MIT.EDU:willc%tekchips.tek.csnet@RELAY.CS.NET Re: multiple values
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To: JAR@AI.AI.MIT.EDU
Cc: rrrs-authors@MC.LCS.MIT.EDU, willc%tekchips.tek.com@RELAY.CS.NET
Subject: Re: multiple values
In-Reply-To: Your message of Fri, 31 Oct 86 21:41:46 EST.
<[AI.AI.MIT.EDU].113058.861031.JAR>
Date: 10 Nov 86 10:53:41 PST (Mon)
From: willc%tekchips.tek.csnet@RELAY.CS.NET
I didn't mean for my message to squelch debate. Surely someone
disagrees with me. Speak up.
Ok, Jonathan. I won't say much because I'm very busy right now. The
message in question:
As Alan has tactfully pointed out to me, none of the multiple-value
features that Gary Brooks and Andy Freeman and I and others have been
talking about bear much resemblance to CL multiple values, and they are
really intended to solve a different problem. The terminology is a
problem here; we really shouldn't be saying that these constructs do
"multiple value returns" because Lisp Machine Lisp and its derivatives
(CL) have been using that term for quite a while to mean something quite
different. (I might have called the LM feature "extra value returns"...)
We should no more think that we're "cleaning up something CL did wrong"
than we should think that omitting optional or keyword arguments,
or macros or packages, solves the problems that those features
were introduced to address.
I see more of a resemblance than Jonathan does. I happen to think that
CL came close to getting multiple values right, failing only in the choice
of primitives, the complexity of the specification (which, as someone has
observed, was due to the fact that CL doesn't do tail recursion right), and
in the over-reliance upon special forms (which is consistent with the rest
of CL).
The main difference between the RECEIVE/VALUES proposals I've seen and
the way CL does it is that people in the Scheme community seem to assume
that most continuations will require exactly one result, while in CL all
continuations accept any number of results (up to 20, anyway). It seems
to me, however, that if you're going to have an efficient implementation
mechanism that supports continuations that accept an arbitrary number of
results, then it shouldn't be too hard to make all continuations accept
an arbitrary number of results. Whether we do this or not should be
determined by whether we think CL got this part of it right.
I like the idea of adding RECEIVE and VALUES to Scheme *without
specifying what happens when some VALUES go somewhere other than to a
RECEIVE*.
Me too. For one thing, it makes it legal for a Scheme to implement
CL-style semantics for multiple values.
Peace, Will
∂10-Nov-86 1904 @MC.LCS.MIT.EDU:ANDY@Sushi.Stanford.EDU silly multiple values
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Date: Mon 10 Nov 86 19:00:15-PST
From: Andy Freeman <ANDY@Sushi.Stanford.EDU>
Subject: silly multiple values
To: rrrs-authors@MC.LCS.MIT.EDU
In-Reply-To: <[AI.AI.MIT.EDU].116160.861108.JAR>
Message-ID: <12253954092.9.ANDY@Sushi.Stanford.EDU>
I once saw a proposal for passing arguments with the name used by the
callee. The idea was that the caller could pass them in any order and
the names provide some documentation. (I think this came up in a
keyword discussion on CommonLisp; KMP, do you remember more? BTW - I
don't think it is a good idea.) For example:
(cons car 'a cdr 'd) = (cons cdr 'd car 'a)
The major problem with using this idea for returning values is
figuring out the inheritance of named values. One possible definition
is the following.
The names of returned values have dynamic scope. The special form
"receive" creates a context for receiving named values. Its first
argument is a list of the names of the values to be received, its
second argument produces them, and following arguments use them.
The special form "establish" has one or more arguments. The first is
a list of name-value pairs. The name is the name of a value to
return, the value is its value. Subsequent arguments are an implicit
begin whose value is the value of the establish form. Establish
should only appear in tail-recursive positions.
Receive and establish can be implemented by the following T syntax
definitions.
(define-syntax (receive names produce . body)
`(apply (lambda , names ,@ body)
(bind , (map (lambda (name) `(, name (undefined)))
names)
, produce
(list ,@ names))))
(define-syntax (establish name-value-pairs . body)
`(begin ,@ (map (lambda (pair) `(set! ,@ pair))
name-value-pairs)
(undefined)
,@ body))
I don't think this is a good proposal but there may be a good way to
use the basic idea. It does allow forms to ignore "extra" values and
(this variation) can be implemented simply.
-andy
-------
∂11-Nov-86 0853 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Scheme errors?
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Date: Tue, 11 Nov 86 11:55:13 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: Scheme errors?
To: RDZ@AI.AI.MIT.EDU
cc: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Tue 11 Nov 86 01:22 EST from Ramin Zabih <RDZ at AI.AI.MIT.EDU>
Message-ID: <[AI.AI.MIT.EDU].117255.861111.JAR>
Date: Tue, 11 Nov 86 01:22 EST
From: Ramin Zabih <RDZ at AI.AI.MIT.EDU>
Have I missed something in my reading of the Scheme report, or is there
in fact no defined way for a program to signal an error?
You didn't miss anything. However, no such mechanism is needed, because
as long as you avoid defining the variable "error", it should simply
work to say (error ...). The effect will be a reference to an unbound
variable, and if the debugging system is halfway decent you'll be able
to see the arguments.
Seriously though, I think most implementations have an "error" procedure
(or special form) which is compatible with S&ICP (and not with CL). But
it might be nice if we in fact standardized on this. Ideally of course
it would be part of a real error (condition) system, though, and it's
possible that that would in turn depend on having fluid variables... I
wouldn't hold my breath...
Jonathan
∂13-Nov-86 0752 @MC.LCS.MIT.EDU:sieber-john@YALE.ARPA Add me to the list
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From: sieber-john@YALE.ARPA
Message-Id: <8611131504.AA00353@yale-celray.YALE.ARPA>
Subject: Add me to the list
To: scheme@mc.lcs.mit.edu
Would you please add me to the Scheme discussion? I was an undergraduate
at Oberlin College where I was infected with the Scheme bug (flavored
heavily by Indiana U. and the Dan Friedman school).
Thanks,
Jack Sieber
sieber@yale.arpa
-------
-------
∂15-Nov-86 1839 @MC.LCS.MIT.EDU:reddy@a.cs.uiuc.edu make-environment
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From: reddy@a.cs.uiuc.edu (Uday S. Reddy)
Message-Id: <8611160233.AA10732@a.cs.uiuc.edu>
To: scheme@mit-mc.arpa
Subject: make-environment
I don't know if this is the right forum to raise this issue. But, I wonder
why make-environment works the way it does. If I define
(define (complex x y)
(make-environment
(define re x)
(define im y)))
(define a (complex 1 2))
not only does a have re and im bound in it, but it also has x and y
bound in it. So,
(access x a)
yields 1. From the description of make-environment in Abelson and Sussman,
it appears that only re and im should be bound in a. Is this a bug, or a
feature, or am I missing something? If this is the way make-environment
is supposed to work, is there some other primitive that binds re and im
and forgets about x and y?
Uday Reddy
∂15-Nov-86 1913 @MC.LCS.MIT.EDU:shneider%cui.unige.chunet%ubc.csnet@RELAY.CS.NET question: S&ICP teacher's manual and query language
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Message-Id: <153:shneider@cui.unige.chunet>
Subject: question: S&ICP teacher's manual and query language
1) We set up group here, disscussing the "structure and interpretation" book
and we'd like to use it for teaching eventually.
Where could I get the teacher's manual ?
(Sorry, if this question has been asked before already)
2) I'd also like to obtain the updated version of the query langauge.
I heard that I might get it from GJS, but I don't know his name
and net address. Anybody does ?
BIG thanks for any help !
∂15-Nov-86 1951 @MC.LCS.MIT.EDU:shneider%cui.unige.chunet%ubc.csnet@RELAY.CS.NET question: S&ICP teacher's manual and query language
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Message-Id: <156:shneider@cui.unige.chunet>
Subject: question: S&ICP teacher's manual and query language
1) We set up group here, disscussing the "structure and interpretation" book
and we'd like to use it for teaching eventually.
Where could I get the teacher's manual ?
(Sorry, if this question has been asked before already)
2) I'd also like to obtain the updated version of the query langauge.
I heard that I might get it from GJS, but I don't know his name
and net address. Anybody does ?
BIG thanks for any help !
-------------------------------------------------------------------------------
Daniel K.Schneider
Departement de science politique, Universite de Geneve
1211 GENEVE 4 (Switzerland), Tel. (..41) (22) 20 93 33 ext. 2357
to VMS/BITNET: to UNIX/EAN (preferable):
BITNET: SCHNEIDER@CGEUGE51 shneider%cui.unige.chunet@CERNVAX
ARPA: SCHNEIDER%CGEUGE51.BITNET@WISCVM shneider%cui.unige.chunet@ubc.CSNET
uucp: mcvax!cernvax!cui!shneider
X.400/ean: shneider@cui.unige.chunet
∂16-Nov-86 1021 @MC.LCS.MIT.EDU:jinx@GENEVA.AI.MIT.EDU make-environment (long)
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From: jinx@GENEVA.AI.MIT.EDU (Guillermo J. Rozas)
Message-Id: <8611161813.AA03965@geneva>
To: reddy@a.cs.uiuc.edu
Cc: scheme@mit-mc.arpa
In-Reply-To: Uday S. Reddy's message of Sat, 15 Nov 86 20:33:52 CST
Subject: make-environment (long)
I don't know if this is the right forum to raise this issue. But, I wonder
why make-environment works the way it does. If I define
(define (complex x y)
(make-environment
(define re x)
(define im y)))
(define a (complex 1 2))
not only does a have re and im bound in it, but it also has x and y
bound in it. So,
(access x a)
yields 1. From the description of make-environment in Abelson and Sussman,
it appears that only re and im should be bound in a. Is this a bug, or a
feature, or am I missing something? If this is the way make-environment
is supposed to work, is there some other primitive that binds re and im
and forgets about x and y?
You have misunderstood section 4.3.1 of S&ICP. If you read it
carefully, you will notice
"For use in conjunction with EVAL, Scheme provides an operation called
MAKE-ENVIRONMENT that constructs an environment, evaluates a
designated sequence of expressions within this environment, and
returns the environment as the value of the MAKE-ENVIRONMENT
expression. The enclosing environment of the new environment is the
environment in which the MAKE-ENVIRONMENT expression was evaluated."
The last sentence in the above quote makes it quite clear that this
environment is built on top of the one in which the MAKE-ENVIRONMENT
expression was evaluated, and therefore all these names are visible to
EVAL.
You ask about ACCESS, which is not in S&ICP, so I assume you are
talking about MIT Scheme instead of the restricted subset used in
S&ICP.
There are two possibilities for ACCESS:
Make it compatible with EVAL, and therefore make all the names (like X
and Y in your example) visible. This is the current implementation.
Make ACCESS look only at the "topmost" frame of the environment. This
means that all the names that can be exported from a package must be
defined in that package itself, and there is no "export" inheritance
between packages built on top of packages.
We tried the latter approach for a while and it was a total mess. We
quickly changed it to its alternative.
∂18-Nov-86 0915 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Scheme reports information request
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Date: Tue, 18 Nov 86 12:14:33 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: Scheme reports information request
To: prlb2!vauclair@SEISMO.CSS.GOV
cc: scheme@MC.LCS.MIT.EDU
In-reply-to: Msg of 18 Nov 86 10:50:34 N (Tue) from Marc Vauclair <prlb2!vauclair at seismo.CSS.GOV>
Message-ID: <[AI.AI.MIT.EDU].119770.861118.JAR>
Date: 18 Nov 86 10:50:34 N (Tue)
From: Marc Vauclair <prlb2!vauclair at seismo.CSS.GOV>
In the "Revised Revised Report on Scheme", I found the following
two little sentences:
on page 5:
"Formal definitions of the lexical and context-free syntaxes of Scheme
will be included in a separate report."
on page 7:
"A formal definition of the semantics of Scheme will be included in a
separate report."
Does those reports exist? Maybe using the same procedure as for the
Revised↑3 Report ?
The "separate report" alluded to actually IS section 7 of the Revised↑3
Report. So the answers are yes and yes, identically.
Jonathan
∂22-Nov-86 1845 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU truncate
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Date: Sat, 22 Nov 86 21:43:12 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: truncate
To: philbin-jim@YALE.ARPA
cc: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <122229.861122.JAR@AI.AI.MIT.EDU>
Date: 22 Nov 86 11:23:34 EST (Sat)
From: James F Philbin <philbin-jim at YALE.ARPA>
To: Rees at YALE.ARPA
Re: truncate
The definition of TRUNCATE in R3RS, p 20., seems ambiguous.
TRUNCATE returns the integer of maximal absolute
value not larger than the absolute value of x.
In the case of -1.1, for example, both 1 and -1 are of maximal
absolute value not larger than the absolute value of -1.1.
I suggest adding the phrase,
... with the same sign as x.
Right.
∂25-Nov-86 1315 @MC.LCS.MIT.EDU:camp%home%ti-csl.csnet@RELAY.CS.NET PC Scheme Utilities
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Date: Tue, 25 Nov 86 14:04:35 cst
From: Clyde Camp <camp%home%ti-csl.csnet@RELAY.CS.NET>
Message-Id: <8611252004.AA13329@>
To: SCHEME@MC.LCS.MIT.EDU
Subject: PC Scheme Utilities
For those of you interested in PCS, a set of free utilities with
documentation is available from:
Clyde R. Camp
Texas Instruments, Inc.
P.O.Box 226015, MS 238
Dallas, TX 75266
Send two blank, FORMATTED disks and a self-addressed, stamped envelope.
Although written primarily for the TIPC, everything except the
graphics should work on and of the IBM clones. The directories are:
UTILITY - Various text windowing, file printing and keyboard handlers
which simplify writing application programs (includes a file
pretty-printer and a new top-level read-eval-print loop which uses an
emacs-like line-editor with the capability to scroll back through
previous entries)
SWI - A convenient mechanism for invoking 8086 ASSY routines via the
rather undocumented SWI-INT.
HELP - A user-extendable on-line help facility which includes all of
the PCS functions and syntax as well as other info
GRAF - A object-style graphics package
PLOT - A general prupose function plotter
GAME1 - Self explanatory - non-graphics
GAME2 - for TIPC graphics
ERR←STAT - more utilities for messing with the status window
MENUSHEL - two menu driven command shells
This should also be available in ARC'd format on COMPUSERVE in the
near future.
- Clyde
∂03-Dec-86 1055 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU Scheme redistribution for BITNET
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Date: Wed, 3 Dec 86 13:12:30 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: Scheme redistribution for BITNET
To: scheme@MC.LCS.MIT.EDU
Message-ID: <125886.861203.JAR@AI.AI.MIT.EDU>
I'm looking for someone on BITNET to volunteer to maintain a BITNET
redistribution list for the Scheme@MC mailing list. This is necessary
because the machine that's acting as the Internet/BITNET gateway,
WISCVM.WISC.EDU, is swamped with mailing list mail. List administrators
(like me) are being asked to set up redistribution lists to help lighten
the load. If we can set one up for Scheme then WISCVM will only have to
relay each message to one host instead of the current 11 or 12 (more in
future).
If you're willing and able to take this on, please let me know.
Thanks...
- Jonathan
∂08-Dec-86 0049 @MC.LCS.MIT.EDU:CPH@AI.AI.MIT.EDU Ambiguity in number syntax
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Date: Mon, 8 Dec 86 03:47:50 EST
From: Chris Hanson <CPH@AI.AI.MIT.EDU>
Subject: Ambiguity in number syntax
To: GJS@AI.AI.MIT.EDU, JAR@AI.AI.MIT.EDU
cc: RRRS-AUTHORS@MC.LCS.MIT.EDU
Message-ID: <127818.861208.CPH@AI.AI.MIT.EDU>
I was trying to implement a parser for the full number syntax in R3RS
and noticed that
#x1234e57
is ambiguous. Does it mean
(* #x1234 (expt 10 57))
or
19091031
Some solutions:
1. Flush scientific notation for hexadecimal numbers. Does anybody
really want to write real numbers (as opposed to integers or
rationals) in hexadecimal?
2. Require an explicit sign character in the exponent for such
numbers. Thus we would say
#x1234e+57
which is unambiguous.
I favor solution (2) since it leaves the syntax as general as
possible.
∂08-Dec-86 0835 @MC.LCS.MIT.EDU:muller@BU-CS.BU.EDU IBM PC Scheme
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From: Robert Muller <muller@BU-CS.BU.EDU>
Message-Id: <8612071341.AA14034@bu-cs.bu.edu>
To: scheme@MC.LCS.MIT.EDU
Subject: IBM PC Scheme
Does anyone know where I can pickup a version of Scheme that runs
on the IBM PC (XT w only 256k)?
thanks,
- Bob Muller
∂08-Dec-86 0934 @MC.LCS.MIT.EDU:HAL%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU IBM PC Scheme
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From: HAL%OZ.AI.MIT.EDU@XX.LCS.MIT.EDU
To: Robert Muller <muller@BU-CS.BU.EDU>
Cc: scheme@MC.LCS.MIT.EDU
Subject: IBM PC Scheme
In-reply-to: Msg of 7 Dec 1986 08:41-EST from Robert Muller <muller at BU-CS.BU.EDU>
Texas instrument's PC scheme runs (barely) in 256K, but you can't
use the editor.
∂08-Dec-86 1016 @MC.LCS.MIT.EDU:jinx@GENEVA.AI.MIT.EDU Ambiguity in number syntax
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From: jinx@GENEVA.AI.MIT.EDU (Guillermo J. Rozas)
Message-Id: <8612081751.AA02460@geneva>
To: CPH@AI.AI.MIT.EDU
Cc: GJS@AI.AI.MIT.EDU, JAR@AI.AI.MIT.EDU, RRRS-AUTHORS@MC.LCS.MIT.EDU
In-Reply-To: Chris Hanson's message of Mon, 8 Dec 86 03:47:50 EST
Subject: Ambiguity in number syntax
There is yet another possibility, which is the one I like best:
#x1234e57
means
(* #x1234 (expt #x10 #x57))
∂09-Dec-86 0812 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU (define foo)
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Date: Tue, 9 Dec 86 11:10:05 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: (define foo)
To: andy@ADS.ARPA
cc: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Sun 7 Dec 86 22:56:01 PST from andy at hobbes.ads.ARPA (Andy Cromarty)
Message-ID: <128392.861209.JAR@AI.AI.MIT.EDU>
Date: Sun, 7 Dec 86 22:56:01 PST
From: andy at hobbes.ads.ARPA (Andy Cromarty)
A lot of MIT code (among other software) seems to contain the cliche'
(define foo) ; Create an unbound instance of FOO
(let ((some-lexical-var 'x)) ; Create a closure....
(set! foo (lambda () ; Define outer FOO to reference
: ; vars visible only in this lexenv.
:
)))
This does not seem to be permitted, even optionally, by the existing R3RS,
as far as I've noticed. Did I miss something, or is it intentional that
(DEFINE FOO) is not permitted, or was it an oversight? I don't recall
having seen discussion of this topic.
If you missed something then I did too. I have no recollection of this
being discussed.
In trying to write portable Scheme code (it's difficult) I find myself
saying things like (define foo 'undefined) pretty often. I don't find
this to be a major inconvenience, but it is an inconvenience. I don't
see any serious problem with the (define foo) construct. It would
presumably mean the same thing as (define foo <undefined>) where
<undefined> is that mysterious expression described in the discussion of
LETREC in section 7.3. A correct immplementation of <undefined> would
of course be 'undefined (or just about anything else), the only
disadvantage of which is that it allow certain error situations to go
undetected.
For symmetry you'd want the syntax to be allowed for both internal
define's and top-level define's. For this to work you'd have to apply the
(define foo) => (define foo <undefined>) rewrite before applying the
define => letrec rewrite.
This feature is implicitly permitted "optionally", because it is a
compatible extension.
Jonathan
∂17-Dec-86 0712 @MC.LCS.MIT.EDU:bartley%home%ti-csl.csnet@RELAY.CS.NET What is comma-dot?
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Date: Tue, 16 Dec 86 13:39:29 cst
From: David Bartley <bartley%home%ti-csl.csnet@RELAY.CS.NET>
Message-Id: <8612161939.AA01741@>
To: RRRS-Authors@MC.LCS.MIT.EDU
Cc: Bartley%home%ti-csl.csnet@RELAY.CS.NET
Subject: What is comma-dot?
Can those of us that permit the destructive splicing operation `,.'
inside quasiquote agree on the symbol it corresponds to? That is, if
,@X is equivalent to (unquote-splicing X), what is ,.X equivalent to?
Perhaps a future R↑nRS should mention this as an extension.
∂31-Dec-86 1100 @MC.LCS.MIT.EDU:NETWORK%FRSAC11.BITNET@WISCVM.WISC.EDU SCOOPS
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Date: Tue, 30 Dec 86 19:30:47 ZONE
To: SCHEME@MC.LCS.MIT.EDU
From: NETWORK%FRSAC11.BITNET@WISCVM.WISC.EDU
Subject: SCOOPS
NETWORK at FRSAC11
To: SCHEME at MC.LCS.M
I just got PC-SCOOPS, (by FTP, courtesy of TI), but I do not run PC-Scheme
but CScheme.... Anybody can help ? (In CScheme there is the rrrs compatibility
package... never tried it, but should be good.)
Sincerly,
+--------------------------------------------------+
| Jean-Pierre H. Dumas |
| Cisi-Telematique |
| CEN Saclay, BP 24 |
| 91190 Gif sur Yvette |
| France |
| |
| Phone: +33 (1) 69 08 46 87 |
| |
| network@frsac11 (bitnet) |
| network%frsac11.bitnet@wiscvm.wisc.edu (arpanet) |
| ..!ihnp4!frsac11.bitnet!network (usenet ?) |
| dumas@sumex-aim.stanford.edu (arpanet) |
+--------------------------------------------------+
∂31-Dec-86 1319 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU What is comma-dot?
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Date: Wed, 31 Dec 86 16:01:03 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: What is comma-dot?
To: bartley%home%ti-csl.csnet@RELAY.CS.NET
cc: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Tue 16 Dec 86 13:39:29 cst from David Bartley <bartley%home%ti-csl.csnet at RELAY.CS.NET>
Message-ID: <135327.861231.JAR@AI.AI.MIT.EDU>
Date: Tue, 16 Dec 86 13:39:29 cst
From: David Bartley <bartley%home%ti-csl.csnet at RELAY.CS.NET>
To: RRRS-Authors at MC.LCS.MIT.EDU
cc: Bartley%home%ti-csl.csnet at RELAY.CS.NET
Re: What is comma-dot?
Message-Id: <8612161939.AA01741@>
Can those of us that permit the destructive splicing operation `,.'
inside quasiquote agree on the symbol it corresponds to? That is, if
,@X is equivalent to (unquote-splicing X), what is ,.X equivalent to?
Perhaps a future R↑nRS should mention this as an extension.
I think this feature is a kludge; I presume you have Common Lisp in
mind. How about "UNQUOTE-SPLICING!" ?
Jonathan
∂31-Dec-86 1333 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU [COMSAT: Msg of Monday, 22 December 1986 16:31-EST]
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Date: Wed, 31 Dec 86 16:01:47 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: [COMSAT: Msg of Monday, 22 December 1986 16:31-EST]
To: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <135329.861231.JAR@AI.AI.MIT.EDU>
Date: Thu, 25 Dec 86 21:08:55 EST
From: Communications Satellite <COMSAT at AI.AI.MIT.EDU>
To: JAR at AI.AI.MIT.EDU
Re: Msg of Monday, 22 December 1986 16:31-EST
Message-ID: <134306.861225@AI.AI.MIT.EDU>
FAILED: rrrs-authors at MC.LCS.MIT.EDU; Host appears to be permanently down or not accepting mail.
Failed message follows:
-------
Date: Mon, 22 Dec 86 16:31:02 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: New, improved quasiquote
To: bartley%home%ti-csl.csnet@RELAY.CS.NET
cc: rrrs-authors@MC.LCS.MIT.EDU
In-reply-to: Msg of Wed 17 Dec 86 16:40:28 cst from David Bartley <bartley%home%ti-csl.csnet at RELAY.CS.NET>
Message-ID: <133673.861222.JAR@AI.AI.MIT.EDU>
Date: Wed, 17 Dec 86 16:40:28 cst
From: David Bartley <bartley%home%ti-csl.csnet at RELAY.CS.NET>
You mailed out a copy of your expand-quasiquote procedure at my
request 13 months ago. Do you have an updated version you could be
persuaded to make public? We never switched over to your algorithm,
but the recent changes to the specification mean we have to rewrite
our quasiquote handler anyway, so it would be nice to continue our
grand tradition of "borrowing" from university sources!
I have several versions. Here is one from which I have removed several
different optimizations. I did this in an attempt to make the code as
simple as possible, without sacrificing too much efficiency. Simpler
versions are possible, as are more optimal ones. E.g. this one won't
generate (vector ...) or (list ...), but it does do maximal sharing of
constant substructure.
You can do (define (system x) x) to get this to work, although in the
Scheme implementation from which this was taken I actually make this
return a funny expression which is an absolute reference to x, so that
things like (let ((cons +)) `(,a b)) works.
- Jonathan
;;; Quasiquote
(define-rewriter 'quasiquote
(lambda (x)
(expand-quasiquote x 0)))
(define (expand-quasiquote x level)
(descend-quasiquote x level finalize-quasiquote))
(define (finalize-quasiquote mode arg)
(cond ((eq? mode 'quote) `',arg)
((eq? mode 'unquote) arg)
((eq? mode 'unquote-splicing)
(error ",@ in illegal context" arg))
(else `(,mode ,@arg))))
(define (descend-quasiquote x level return)
(cond ((vector? x)
(descend-quasiquote-vector x level return))
((not (pair? x))
(return 'quote x))
((interesting-to-quasiquote? x 'quasiquote)
(descend-quasiquote-pair x (1+ level) return))
((interesting-to-quasiquote? x 'unquote)
(cond ((= level 0)
(return 'unquote (cadr x)))
(else
(descend-quasiquote-pair x (- level 1) return))))
((interesting-to-quasiquote? x 'unquote-splicing)
(cond ((= level 0)
(return 'unquote-splicing (cadr x)))
(else
(descend-quasiquote-pair x (- level 1) return))))
(else
(descend-quasiquote-pair x level return))))
(define (descend-quasiquote-pair x level return)
(descend-quasiquote (car x) level
(lambda (car-mode car-arg)
(descend-quasiquote (cdr x) level
(lambda (cdr-mode cdr-arg)
(cond ((and (eq? car-mode 'quote) (eq? cdr-mode 'quote))
(return 'quote x))
((eq? car-mode 'unquote-splicing)
;; (,@mumble ...)
(cond ((and (eq? cdr-mode 'quote) (null? cdr-arg))
(return 'unquote
car-arg))
(else
(return (system 'append)
(list car-arg (finalize-quasiquote cdr-mode cdr-arg))))))
(else
(return (system 'cons)
(list (finalize-quasiquote car-mode car-arg)
(finalize-quasiquote cdr-mode cdr-arg))))))))))
(define (descend-quasiquote-vector x level return)
(descend-quasiquote (vector->list x) level
(lambda (mode arg)
(case mode
((quote) (return 'quote x))
(else (return (system 'list->vector)
(list (finalize-quasiquote mode arg))))))))
(define (interesting-to-quasiquote? x marker)
(and (pair? x) (eq? (car x) marker)))
∂05-Jan-87 0803 @MC.LCS.MIT.EDU:NETWORK%FRSAC11.BITNET@WISCVM.WISC.EDU SYMBOLIC COMPUTATION.
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at 09:57:19 CST
Date: Wed, 31 Dec 86 16:27:48 ZONE
To: SCHEME@MC.LCS.MIT.EDU
From: NETWORK%FRSAC11.BITNET@WISCVM.WISC.EDU
Subject: SYMBOLIC COMPUTATION.
NETWORK at FRSAC11
To: SCHEME at MC.LCS.M
Does anybody know about a Scheme package to do symbolic computation ??
(a la Reduce, Macsyma...)
P.S. I run CScheme on UTS/V.
Happy new year.
+--------------------------------------------------+
| Jean-Pierre H. Dumas |
| Cisi-Telematique |
| CEN Saclay, BP 24 |
| 91190 Gif sur Yvette |
| France |
| |
| Phone: +33 (1) 69 08 46 87 |
| |
| network@frsac11 (bitnet) |
| network%frsac11.bitnet@wiscvm.wisc.edu (arpanet) |
| ..!ihnp4!frsac11.bitnet!network (usenet ?) ∀
| dumas@sumex-aim.stanford.edu (arpanet) |
+--------------------------------------------------+
∂05-Jan-87 2047 @MC.LCS.MIT.EDU:willc%tekchips.tek.com@RELAY.CS.NET Re: What is comma-dot?
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To: JAR@AI.AI.MIT.EDU, bartley%home%ti-csl.csnet@RELAY.CS.NET
Cc: adams%tekchips.tek.com@RELAY.CS.NET, rrrs-authors@MC.LCS.MIT.EDU
Subject: Re: What is comma-dot?
In-Reply-To: Your message of Wed, 31 Dec 86 16:01:03 EST.
<135327.861231.JAR@AI.AI.MIT.EDU>
Date: 05 Jan 87 12:58:13 PST (Mon)
From: willc%tekchips.tek.com@RELAY.CS.NET
Just as standardization can be a destructive force, by encouraging the use
of standardized but doubtful features, so can lack of standardization be a
creative force, by discouraging use of non-standardized doubtful features.
I consider comma-dot an excellent candidate for non-standardization.
Will
∂06-Jan-87 0824 @MC.LCS.MIT.EDU:bartley%home%ti-csl.csnet@RELAY.CS.NET What is comma-dot?
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Date: Tue, 6 Jan 87 08:46:09 cst
From: David Bartley <bartley%home%ti-csl.csnet@RELAY.CS.NET>
Message-Id: <8701061446.AA20269@>
To: RRRS-Authors@MC.LCS.MIT.EDU
Subject: What is comma-dot?
> From: David Bartley <bartley@home>
>
> Can those of us that permit the destructive splicing operation `,.'
> inside quasiquote agree on the symbol it corresponds to? That is, if
> ,@X is equivalent to (unquote-splicing X), what is ,.X equivalent to?
> Perhaps a future R↑nRS should mention this as an extension.
> From: willc@tekchips.tek.com
>
>Just as standardization can be a destructive force, by encouraging the use
>of standardized but doubtful features, so can lack of standardization be a
>creative force, by discouraging use of non-standardized doubtful features.
>I consider comma-dot an excellent candidate for non-standardization.
Will seems to have stated the consensus, if the other replies to my
original message are representative. I will adopt JAR's suggested
name, UNQUOTE-SPLICING!, but agree that this is a "doubtful" feature
and that standardization isn't called for.
∂10-Jan-87 1130 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU 2nd test
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Date: Sat, 10 Jan 87 14:15:10 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: 2nd test
To: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <138728.870110.JAR@AI.AI.MIT.EDU>
This is a second test message for today, which everyone should feel at
liberty to ignore.
∂16-Jan-87 0850 @MC.LCS.MIT.EDU:dfried%iuvax.cs.indiana.edu@RELAY.CS.NET multiple values and T
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Date: Fri, 16 Jan 87 09:56:21 est
From: Dan Friedman <dfried%iuvax.cs.indiana.edu@RELAY.CS.NET>
To: rrrs-authors%mit-mc.CSNET@RELAY.CS.NET
Subject: multiple values and T
Here is the material taken from "T Version 3.0 Release Notes" concerning
multiple return values. Following this material will be a short example
which demonstrates how this could be made more general.
Version 3.0 of T supports multiple return values. This makes procedure
call and return uniform, in te sense that a procedure can be invoked with
zero or more values and can return zero or more values.
(return {value}*) ==> {value}* procedure
return returns its arguments as the values(s) of the current expression.
In order to access the value(s) of a return expression the value(s) must be
bound to identifiers using either receive or receive-values.
For example,
((lambda () (return 1 2 3))) ==> 1 2 3
where "==> 1 2 3" denotes evaluates to the three values 1, 2, and 3.
return when invoked with no arguments returns to the calling procedure with
no value. Thus (return) will return to its caller with no value. It is an
error to return no value to a value requiring poisition. For example,
(list 'a (return)) ==> error
The idiom (return) is useful for procedures that return an undefined value and
many of the system procedures whose value(s) is(are) undefined now return no
value. However, the procedure undefined-value may provide a more informative
error message.
(receive-values receiver sender) procedure
==> value(s) of receiver
receive-values returns the value of applying receiver, a procedure of n
arguments, to the values returned by sender. sender is a thunk, a procedure
of no arguments, which returns n values.
For example,
(receive-values (lambda (x y) (list x y))
(lambda () (return 1 2))) ==> (1 2)
(receive ({ident}*) expression {body}*) syntax
==> value of body
In a receive form the expression is evaluated in the current environment
and the values returned by the expression are bound to the corresponding
identifiers. body, which should be a lambda body, i.e. a sequence of one
or more expressions, is evaluated in the extended environment and the
value(s) of the last expression in body is returned.
The expression
(receive (a b c) (return 1 2 3)
(list a b c))
==> (1 2 3)
is equivalent to
(receive-values (lambda (a b c) (list a b c))
(lambda () (return 1 2 3)))
==> (1 2 3)
Other froms have been extended in T3.0 to allow multiple return values.
(catch identifier {body}*) ==> value of body syntax
The identifier is bound to the continuation of the catch form, which is now
an n-ary procedure. This means that catch forms can return multiple values.
The continuation can be invoked only during the dynamic extent of the catch
form. In T2 the continuation was a procedure of one argument. For example,
(catch x (list 1 (x 2 3) 4)) ==> 2 3
(ret {value}*) ==> {value}* procedure
returns zero or more values as the value of the current read-eval-print loop.
Note: Multiple values are implemented efficiently. It may be more efficient
to use multiple values than to pass continuations.
End of disccusion from the Relases Notes.
What disturbs me is the way that it does not seem to be as general as it
could be. What I would like to propose is the ability to splice in return
values. Here is an example:
((lambda (a b c q x y) ...)
(return 1 2 3) 4 (return 5 6)).
It is possible that this capability is exactly what T Version 3.0 does.
However, there were no examples of this type so I believe this has been
overlooked.
I know that when we met in Cambridge Jonathan offered to work on multiple
values. This is something for all of us to consider.
Dan
∂16-Jan-87 1400 @MC.LCS.MIT.EDU:hudak-paul@YALE.ARPA Re: multiple values and T
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Date: Fri, 16 Jan 87 16:22:37 est
From: Paul Hudak <hudak-paul@YALE.ARPA>
Message-Id: <8701162122.AA06172@yale-eli.YALE.ARPA>
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Subject: Re: multiple values and T
To: Dan Friedman <dfried%iuvax.cs.indiana.edu@RELAY.CS.NET>
Cc: rrrs-authors@mc.lcs.mit.edu
In-Reply-To: Dan Friedman <dfried%iuvax.cs.indiana.edu@RELAY.CS.NET>, Fri, 16 Jan 87 09:56:21 est
...
End of disccusion from the Relases Notes.
What disturbs me is the way that it does not seem to be as general as it
could be. What I would like to propose is the ability to splice in return
values. Here is an example:
((lambda (a b c q x y) ...)
(return 1 2 3) 4 (return 5 6)).
It is possible that this capability is exactly what T Version 3.0 does.
However, there were no examples of this type so I believe this has been
overlooked.
No, T does not do this (by design). The problem is that it's not always
obvious what the bindings are. For example, replace the above two
occurrences of RETURN with calls to unknown procedures:
((lambda (a b c q x y) ...)
(f) 4 (g))
The problem with this is that one cannot tell, looking at this code alone,
which bound variable 4 is bound to. Indeed, different invocations of this
may induce different bindings, depending on the bindings of f and g! This
seems to us to violate one's notion of referential transparency.
Paul Hudak
David Kranz
Richard Kelsey
-------
∂16-Jan-87 1645 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU multiple values
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Date: Fri, 16 Jan 87 19:45 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: multiple values
To: rrrs-authors@MC.LCS.MIT.EDU
Message-ID: <870116194506.1.JAR@ROCKY-GRAZIANO.LCS.MIT.EDU>
Maybe some of you missed or have forgotten the relevant discussion last
October and November, so here's a digest. If you remember this stuff,
you needn't examine this message any further, and I apologize for
cluttering your mailboxes.
The mechanism in T3 is essentially the same as that presented in my
message of Thu, 30 Oct 86 22:08:03 EST. That message also includes some
motivation, which I won't repeat here, and Dan has already sent out the
technical content. The rather important detail ommitted from the T3
release notes is that it's an error whenever the number of values
expected doesn't match the number delivered, and argument and predicate
positions expect exactly one value. Thus (list (return 1 2)) is an
error in T3 and in my proposal.
The mechanism that Dan Friedman proposes was suggested on this list by
Andy Freeman:
Date: Thu 30 Oct 86 12:25:22-PST
From: Andy Freeman <ANDY@Sushi.Stanford.EDU>
This proposal is a variant on the technique Carolyn Talcott used
in her thesis; Richard Weyrauch was also involved in that work.
Their idea requires one procedure; I'll call it values. Procedure
invocation spreads multiple values; (cons (values 1 2)) is completely
equivalent to (cons 1 2) and (list (values) 4 (values 1 2) 3) is
equivalent to (list 4 1 2 3). ...
It was dismissed by the only people on the list (besides maybe Sussman)
who had actual experience using it, namely Steele and Gabriel:
Date: Mon, 3 Nov 86 11:24 EST
From: Guy Steele <gls@Think.COM>
It [MARVEL] did pretty much all the obvious things: every function
call was implicitly like the Common Lisp MULTIPLE-VALUE-CALL, and
most side-effecting forms such as SETQ, PRINT, and COMMENT were made
to return zero values. I believe I also arranged for variables to
be able to hold multiple values.
My experience with the language was that it was perfectly clean
and elegant, but programs that made non-trivial use of multiple
values were very hard to read, precisely because of the loss
of the one-form/one-value correspondence. Having the extra power
everywhere in the language was not worth the loss of clarity.
I therefore abandoned the experiment without writing it up.
(Maybe I should have, but there were other, more promising variations
of Scheme to explore.)
...
I believe that experience with the POP languages (especially POP-2)
may be relevant to this discussion, but I am not an expert there.
Date: 03 Nov 86 1214 PST
From: Dick Gabriel <RPG@SAIL.STANFORD.EDU>
...
The code, as Steele mentions, was elegant in a certain sense, but
very hard to read most of the time, because you had to take into
account that some other values than the primary value (the first
one) would be passed to some program. The places where SEUS code
was easy to read were when you were writing something that, in
Common Lisp, would be
(multiple-value-call #'foo (baz) (bar))
The places where it was hard to read were when you were writing something
that, in Common Lisp, would be
(foo (baz) (bar))
That is, there was no easy way to check that the right values from the
right places got passed. I think that the latter is the more commonly
used case, so SEUS was optimized the wrong way.
...
When the Common Lisp multiple value scheme was being devised, I thought
that we (the designers) should look at SEUS for its experience. I'm now
glad we didn't do anything more that invent MULTIPLE-VALUE-CALL as a
result of that experience.
I tend to agree that it's a bad idea, not only from the point of view of
someone using it, but also for implementation reasons: unlike the T
proposal, which is trivially implementable (VALUES = LIST) in any scheme
implementation, it's grossly incompatible with current implementations;
and it has a performance cost that you have to always pay for, even when
you're not using the feature, because all calls to unknown procedures
must be prepared to splice in an arbitrary amount of crud.
Jonathan
∂16-Jan-87 1656 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU [vanroggen%bizet.DEC: LISP POINTERS newsletter announcement]
Received: from MC.LCS.MIT.EDU by SAIL.STANFORD.EDU with TCP; 16 Jan 87 16:56:12 PST
Received: from AI.AI.MIT.EDU (CHAOS 3130) by MC.LCS.MIT.EDU 16 Jan 87 19:48:29 EST
Date: Fri, 16 Jan 87 19:51:30 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: [vanroggen%bizet.DEC: LISP POINTERS newsletter announcement]
To: scheme@MC.LCS.MIT.EDU
Message-ID: <141187.870116.JAR@AI.AI.MIT.EDU>
Apologies to those of you who are on both SCHEME and COMMON-LISP.
Date: Friday, 16 Jan 1987 06:42:06-PST
From: vanroggen%bizet.DEC at decwrl.DEC.COM
To: common-lisp at sail.stanford.edu,
vanroggen%bizet.DEC at decwrl.DEC.COM
Re: LISP POINTERS newsletter announcement
Message-Id: <8701161443.AA21565@decwrl.dec.com>
*** ANNOUNCEMENT ***
LISP POINTERS
We're putting together a newsletter and we'd like you to come along.
Every other month, starting in March of 1987, Lisp Pointers will
be bringing you articles, implementation summaries, opinion columns,
and information on the lastest action on the standardization front.
And we need you -- to contribute to our departments, to read the
results of our efforts, and to suggest ways we can provide more of the
kinds of information you want to see.
Lisp Pointers is being funded by companies who care about the future
of Lisp. The editorial content of the newsletter will not be
influenced by these companies nor will the companies be responsible
for the material contained within Lisp Pointers. Until such time as
we affiliate with a more formal organization, subscriptions to Lisp
Pointers will be free. Please spread the word among your friends,
both real and electronic.
Our newsletter will be available through the mails. To join our
mailing list, send your name and address to:
Mary S. Van Deusen, Editor
IBM Research
PO Box 704
Yorktown Heights, New York 10598
914-789-7845
617-384-2526
MAIDA@IBM.COM
Contributions should be sent directly to the appropriate department:
***LETTERS TO THE EDITOR, NEWS ITEMS***
Mary S. Van Deusen (see above)
***IMPLEMENTATIONS***
Walter van Roggen
DEC
77 Reed Road
HL02-3/E9
Hudson, Massachusetts 01749
617-568-5617
VANROGGEN%BACH.DEC@DECWRL.DEC.COM
***BOOK REVIEWS, BIBLIOGRAPHIES***
Daniel Weinreb
Symbolics, Inc.
11 Cambridge Center
Cambridge, Massachusetts 02142
617-577-7500
DLW@MC.LCS.MIT.EDU
***X3J3 LISP STANDARDIZATION***
Robert F. Mathis
9712 Ceralene Drive
Fairfax, Virginia 22032
703-425-5923
mathis@b.isi.edu
***USERS***
Susan Ennis
Amoco Production Co.
PO Box 3385
Tulsa, Oklahoma 74102
918-660-3588
***TECHNICAL ARTICLES***
Jonl White
Lucid, Inc.
707 Laurel Street
Menlo Park, California 94025
415-329-8400
edsel!bhopal!jonl@navajo.stanford.edu
***ENVIRONMENTS***
John Foderaro
Franz Inc.
1141 Harbor Bay Parkway
Suite 270
Alameda, California 94501
415-769-5656
jkf%franz.uucp@berkeley.edu
***SCHEME***
Will Clinger M/S 50-662
Tektronics Inc.
PO Box 500
Beaverton, Oregon 97077
willc%tekchips@tek.csnet
503-627-4675
***LISP QUESTIONS***
Patrick Dussud
Texas Instruments
12501 Research Boulevard
MS 2201
Austin, Texas 78759
dussud%jenner%ti-csl.csnet@csnet-relay
***INTERNATIONAL ISSUES***
Christian Quiennec
LITP
4 Place Jussieu
F-75252, Paris Cedex 05
FRANCE
tel: +33 (1) 43 36 25 25 x 5251
UUCP: ..!mcvax!inria!queinnec
ARPA: mcvax!inria!queinnec@seismo.css.GOV
∂18-Jan-87 2027 @MC.LCS.MIT.EDU:ramsdell%faron@mitre-bedford.ARPA Scheme time
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Received: from mitre-bedford.ARPA (TCP 3200600102) by MC.LCS.MIT.EDU 18 Jan 87 23:26:54 EST
Organization: The MITRE Corp., Bedford, MA
Received: by faron.MENET (4.12/4.7)
id AA10400; Sun, 18 Jan 87 23:25:14 est
Date: Sun, 18 Jan 87 23:25:14 est
From: John D. Ramsdell <ramsdell%faron@mitre-bedford.ARPA>
Posted-Date: Sun, 18 Jan 87 23:25:14 est
Message-Id: <8701190425.AA10400@faron.MENET>
To: rrrs-authors%mc.lcs.mit.edu@mitre-bedford.ARPA
Subject: Scheme time
I noticed there is no standard time function for scheme.
Let me propose the following:
(days-after-J2000.0) => current time in units of days
as a floating point number. The time origin is noon,
January 1, 2000. This date is called J2000.0 by astronomers,
and represents a good time origin for those who are interested
in computing the position of the sun and other stars. For
example, a formula that gives the approximate location of the
sun in these units is in "The Astronomical Almanac for the Year
1984", US Naval Observatory and Royal Greenwich Observatory,
US Government Printing Office, Washington DC, 1984.
John
∂25-Jan-87 1837 @MC.LCS.MIT.EDU:JAR@AI.AI.MIT.EDU [vanroggen%bach.DEC: Looking for Lisps...]
Received: from MC.LCS.MIT.EDU by SAIL.STANFORD.EDU with TCP; 25 Jan 87 18:36:48 PST
Received: from AI.AI.MIT.EDU (CHAOS 3130) by MC.LCS.MIT.EDU 25 Jan 87 21:34:00 EST
Date: Sun, 25 Jan 87 21:32:13 EST
From: Jonathan A Rees <JAR@AI.AI.MIT.EDU>
Subject: [vanroggen%bach.DEC: Looking for Lisps...]
To: scheme@MC.LCS.MIT.EDU
Message-ID: <144637.870125.JAR@AI.AI.MIT.EDU>
Apologies to those of you who have seen this message already.
I have nothing to do with this newsletter; I'm just forwarding this
message because I thought people on the scheme list might be interested.
- Jonathan
Date: Tuesday, 20 Jan 1987 14:48:29-PST
From: vanroggen%bach.DEC at decwrl.DEC.COM
To: common-lisp at sail.stanford.edu,
vanroggen%bach.DEC at decwrl.DEC.COM
Re: Looking for Lisps...
Message-Id: <8701202249.AA09113@decwrl.dec.com>
As part of a feature of the LISP POINTERS newsletter, we'd like to collect
descriptions of all currently available Lisp implementations.
Any kind of Lisp is acceptable; it doesn't have to be Common Lisp or Scheme or
Interlisp or MacLisp. It doesn't have to be a commercially supported product
either; it can be free with no warranties whatsoever.
If you're working on an implementation, and you're willing to describe it
for everyone's benefit, send us at least the following information:
Implementation Name
Implemented to which standard (if any)
Features (if no standard; see the suggested list of issues below)
Additional Features (if implemented according to a standard)
Missing Features (if implemented according to a standard)
Current version/availability/prices
Support (if supported, by whom; sources available?)
Machine(s)
Operating System(s)
Source or Contact
Any other comments
Submitter's name, address, and net-address
Some features you might want to comment on include:
Predefined data types
Name spaces and scopes and extents
Control structures (e.g., special forms, non-local goto's, multiple
values, multiple stacks, tasking, multi-processor support)
Typing and declarations
Garbage collection
I/O functions
Compiler
Object-oriented support
Graphics and windowing support
Programming tools (e.g., graphics packages, editor interaction,
system maintenance)
Interaction with other languages
AI-oriented tools (e.g., pattern matching, rules, database support,
natural language interface)
Any other interesting features
Send this information to:
Walter van Roggen
Net address: VANROGGEN%BACH.DEC@DECWRL.DEC.COM
Mail address: HLO2-3/E9, 77 Reed Rd, Hudson MA, 01749, USA