March 17, 2003

Chris Double has a nice post about Screamer, the non-deterministic programming system (which he ported to Corman Lisp).

I'd heard of Screamer but had always thought it to be a very difficult product which would be hard to port. In fact, it was almost trivial. It's all done with macros. Basically it walks the code you write using macros looking for non-deterministic function calls. When these are found it converts that code to continuation-passing-style and uses these continuations to implement backtracking, etc. It's very clever but you don't need to know anything about the implementation to use it.

Screamer seems like a nice example of the ability to extend the lisp language with macros.

Posted by jjwiseman at March 17, 2003 08:34 PM

It's true that Screamer is a thought-provoking and fun package. However, as someone who has tried to use it, I would say that it's also true that it's almost completely useless.
The problem is that heavily macro-doctored code doing search is essentially completely undebuggable. Especially when it makes very heavy use of context structure.
I wanted to like Screamer, but I just couldn't.

Posted by: Robert Goldman on April 8, 2003 10:42 AM
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