[Haskell-cafe] Re: Is Haskell a 5GL?

Bill Wood william.wood3 at comcast.net
Mon Sep 25 17:03:02 EDT 2006

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

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