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␈↓ ↓H␈↓␈↓βS␈↓∧ Artificial Intelligence Laboratory, STANFORD UNIVERSITY, Stanford, California 94305

␈↓ ↓H␈↓∧Telephone 415 497-4430␈↓ 
⊃April 16, 1979 




␈↓ ↓H␈↓Dr. John Williams
␈↓ ↓H␈↓IBM Research
␈↓ ↓H␈↓K52-282
␈↓ ↓H␈↓5600 Cottle Road
␈↓ ↓H␈↓San Jose, CA 95193

␈↓ ↓H␈↓Dear Dr. Williamson:

␈↓ ↓H␈↓        Thanks for the invitation to talk at IBM Research.  Here is the abstract.

␈↓ ↓H␈↓THE ELEPHANT ALGORITHMIC LANGUAGE

␈↓ ↓H␈↓        Elephant␈α∃(it␈α⊗never␈α∃forgets)␈α⊗is␈α∃a␈α∃new␈α⊗proposed␈α∃algorithmic␈α⊗language␈α∃(perhaps␈α⊗not␈α∃a
␈↓ ↓H␈↓programming␈αlanguage)␈αwith␈α
two␈αproperties.␈α First,␈α
like␈αa␈αLucid␈α
program,␈αan␈αElephant␈αprogram␈α
is
␈↓ ↓H␈↓a␈αcollection␈αof␈αstatements␈αin␈α≡rst␈αorder␈αlogic␈αwhich␈αcan␈αbe␈αused␈αdirectly␈αto␈αprove␈αproperties␈αof␈αthe
␈↓ ↓H␈↓program.␈α∂ Unlike␈α∂Lucid,␈α∂Elephant␈α∂programs␈α∂refer␈α⊂directly␈α∂to␈α∂the␈α∂time;␈α∂i.e.␈α∂each␈α∂variable␈α⊂in␈α∂an
␈↓ ↓H␈↓Algolic␈α∩program␈α∩is␈α∩replaced␈α∪by␈α∩a␈α∩function␈α∩of␈α∪time␈α∩in␈α∩the␈α∩corresponding␈α∪Elephant␈α∩program.
␈↓ ↓H␈↓Second,␈αElephant␈αprograms␈αcan␈αrefer␈αdirectly␈αto␈αthe␈αpast␈αof␈αvariables,␈αand␈αit␈αis␈αup␈αto␈αthe␈α
compiler
␈↓ ↓H␈↓to␈α∞decide␈α∞what␈α∞data␈α∞structures␈α
have␈α∞to␈α∞be␈α∞kept␈α∞in␈α
order␈α∞to␈α∞achieve␈α∞the␈α∞speci≡ed␈α∞behavior.␈α
 For
␈↓ ↓H␈↓example,␈α∞an␈α∂Elephant␈α∞reservation␈α∂program␈α∞can␈α∂specify␈α∞that␈α∞a␈α∂person␈α∞has␈α∂a␈α∞reservation␈α∂(for␈α∞an
␈↓ ↓H␈↓Elephant␈αride)␈αif␈αhe␈αhas␈αsuccessfully␈αmade␈αone␈αand␈αit␈αhasn't␈αbeen␈αcancelled.␈α On␈αthe␈αbasis␈αof␈αthe
␈↓ ↓H␈↓prescribed␈α∀input-output␈α∀behavior,␈α∀the␈α∃compiler␈α∀must␈α∀decide␈α∀that␈α∀cancelled␈α∃reservations␈α∀and
␈↓ ↓H␈↓unsuccessful attempts to reserve needn't be remembered.

␈↓ ↓H␈↓        An␈αElephant␈αcompiler␈α-␈αnone␈αpresently␈αexists␈α-␈αwill␈αhave␈αto␈αbe␈αa␈αheuristic␈αprogram,␈αand␈α
the
␈↓ ↓H␈↓utility␈αof␈αthe␈αlanguage␈αdepends␈αon␈αwhether␈αa␈αgood␈αone␈αcan␈αbe␈αwritten.␈α If␈αit␈αcan␈αElephant␈αwill␈αbe
␈↓ ↓H␈↓a very high level language.


␈↓ ↓H␈↓Sincerely,



␈↓ ↓H␈↓John McCarthy
␈↓ ↓H␈↓Director
␈↓ ↓H␈↓Professor of Computer Science