Re: Thus spake the DoD...

[djsalomon@watdaisy.UUCP (Daniel J. Salomon)]

> The way we say it around here is "most programs written in *other* languages
> could be written better in Lisp" - that includes work in VLSI, graphics,
> compilers, algebra, and suchlike.  Name me ONE thing that Pascal or Ada
> does better than Lisp (besides `confuse and frustrate the programmer')...
> 
> 							stan shebs

Since LISP is a typeless language a LISP interpreter or compiler will
accept almost any meaningless input (in which the parentheses match)
as a valid program.  Thus the correctness of programs must be proved by
exhaustive test cases or by theoretical analysis.  Although LISP is
more amenable to theoretical analysis than most languages, let's face
it, most LISP programmers would rather hack out another test case than
do any analysis.

Since LISP uses function notation for all operations it is a simple
language to implement and a simple language in which to automatically
generate code (thus the AI connection).  Similarly its use of lists to
implement all data types and all structures is a simple and interesting
concept.  But these two features have made LISP one of the most
inefficient languages in existence.  In many ways this inefficiency
has hindered the development of AI.  People now associate AI with
programs that are too costly to run.

This inefficiency has led LISP programmers on an endless search for
more powerful hardware.  The search may lead to new and exciting
parallel architectures but until they are designed and built we should
find ways to make good use of the hardware we have.

Writing in LISP is challenging and fun.  It's simplicity both liberates
and constrains the programmer so that writing LISP programs is
something like solving a puzzle or playing chess.  Many intelligent
people enjoy this aspect of LISP.  Unfortunately LISP programs remain a
puzzle even after they are written.  LISP programs are both
syntactically and logically hard to document.  Usually only the
original author will fully understand how a LISP program works, and
after a few years not even he will.

I thus stand by my original claim that the importance of LISP to AI is
greatly exaggerated.  Not only can one now chose one of the LISP
offspring such as PROLOG or FORTH, but also if one is writing an actual
production system one should examine one of the more efficient
algorithmic languages to see if it is adequate for one's application.