~F8LISP INTERFACING TO CRE.

	It should be possible  to embed the CRE machine  code under a
LISP  core image; however I  do not intend  to do this  work. For the
present, the CRE interface to LISP  is only realized via a disk  file
transfer of  the data structure.   A CRE file  may be read  into LISP
binary  program space  and accessed  using the CRE  nomensclature (11
link  names  and  13  datum  names)  by  means  of  the  S-Expression
subroutines provided  in the file CRE.LSP[CRE,BGB].   The subroutines
work in both the old Stanford LISP 1.6 as well as the newer UCI  LISP
and Micro Planner, PLNR. The CRE.LSP[CRE,BGB] can be loaded either by
one or the other of the following tWo LISP statements:

	(DSKIN(CRE,BGB)(CRE.LSP))
	(INC(INPUT(CRE,BGB)(CRE.LSP)))

A CRE film file is read into LISP binary program space by one of the
three possible INCRE formats:

	(INCRE filename)
	(INCRE filename project)
	(INCRE filename project programmer)

Filenames should be  six characters or less, projects  and programmer
initials should  be three characters or  less, the filename extension
CRE is  assummed and the  usual PPPN  defaults  occur. If  the  input
succeeds INCRE returns a value T;  if the input fails INCRE returns a
value NIL and prints one or the other of these two messages:

	CRE FILE NOT FOUND.
	CRE FILE REQUIRES 00000 MORE WORDS OF BINARY PROGRAM SPACE.

After a sucessful  INCRE; the film,  image,  level, polygon,  arc and
vector  nodes are  referred to  by integers using  the 11  Link Fetch
Subroutines:
	(CW node)(CCW node)(DAD node)(SON node)(ENDO node)(EXO node)
	(ALT node)(NGON node)(PGON node)(NTIME node)(PTIME node)

The film  node's  address is  the  integer 0,   zero.    So that  the
expression  (SETQ V3(CCW(CCW(SON(SON(SON(SON  0)))))))  will retrieve
the lower right hand corner of the border polygon of the -1  level of
the first image  of the film. The 13 CRE.LSP  datum fetch subroutines
are:
	(ROW node)(COL node)(CRETYPE node)(RELOC node)
	(CNTRST node)(NCNT node)(ZDEPTH node)(PERM node)(AREA node)
	(MXX node)(MYY node)(MZZ node)(PXY node)
~I1973,800;F8- 40 -