On Mon, 2006-09-25 at 22:22 +0200, Christoph Herrmann wrote: . . .
What Prolog really provides concerning automatic problem solving is little: equation solving in term algebra; you can simulate that in Haskell without much effort. On the other hand, I saw Haskell classified as a 3GL. The problem is that Haskell often exposes the algorithmic structure. What people often forget is that Prolog programs in non-trivial situations are likely to fail if you do not prescribe the evaluation order, by features like the cut which destroy the declarative semantics. People also forget that arithmetic constraints in Prolog have to be directed (input/output variables), no difference to Haskell.
I spent some time working on a large Prolog application where performance was critical, and it became obvious that when a Prolog program is tuned by removing non-determinism it moves towards a functional program. Any real (non-textbook example) Prolog program has to expose algorithmic details simply because the programmer must a) make decisions and b) express them. I think you're right that Haskell should be in the same bag as Prolog. -- Bill Wood