RE: Screamer ported to Corman Lisp.

Seeing Screamer reminded me of the Icon language
http://www.cs.arizona.edu/icon/ that has backtracking built into it.
Their intro says:
"Icon is a very high level general-purpose programming language with
extensive features for processing strings (text) and data structures. Icon
is an imperative, procedural language with a syntax that is reminiscent of C
and Pascal, but with semantics at a much higher level. 

Icon has a novel expression-evaluation mechanism that integrates
goal-directed evaluation and backtracking with conventional control
structures. ..."

In Icon the backtracking is applied to goal directed programs - which for
Icon traditionally
involved text matching with the evaluation backtracking out of various
partial matches to
arrive eventually at a final match(or matches). It is also (in my mind at
least) closely linked to
the use of generators in Icon that iterate over some structure or result
space.
Perhaps if you look at backtracking in Icon it would give you ideas for
using Screamer.

A couple of Icon related discussions of backtracking are:
http://www.nmt.edu/tcc/help/lang/icon/backtrack.html
http://www.cs.arizona.edu/icon/analyst/backiss/IA54.pdf A discussion
relating to problematic aspects of backtracking

Regards
Nigel

-----Original Message-----
From: Arthur Lemmens [mailto:alemmens@xxxxxxxxx] 
Sent: Wednesday, 12 March 2003 7:17 AM
To: cormanlisp@xxxxxxxxxxxxxxx
Subject: Re: [cormanlisp] Screamer ported to Corman Lisp.



Chris Double wrote:
> 
> I've ported Screamer to Corman Lisp 2.01. Screamer is a library for 
> Common Lisp that provides support for non-deterministic programming. 
> This includes backtracking, undoable side effects and constraint 
> programming. For details and download location see:
> 
>   http://radio.weblogs.com/0102385/2003/03/12.html#a309

Thanks for the links to Screamer+. I've played a bit with Screamer before,
but I'd never seen Screamer+. Could you describe the problem(s) for which 
you're using Screamer? Although I like the idea of non-deterministic 
programming in Common Lisp, I've never found a use for it in my own
programs. 
But I suspect that this is just a lack of imagination and experience on my 
part, so I'm very interested in real-life examples of non-deterministic 
Lisp programming.

Thanks.

Arthur Lemmens

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