Re: Curry design

From: Michael Hanus <hanus_at_I2.Informatik.RWTH-Aachen.DE>
Date: Thu, 3 Jul 1997 18:11:58 +0200

John Lloyd wrote:
> Well if Haskell is a subset of Escher and Escher is a subset of Curry,
> then Curry also includes Haskell. QED. This isn't the point. Haskell is
> already very expressive. Escher adds logic programming facilities powerful
> enough to easily encode typical Prolog-like programs together with sets.
> Do we need to go further? I really think we can argue at the abstract
> level forever on this - what we need are some concrete programs. And I think
> the ball is in the narrowing court. I say rewriting is enough. Let's see
> the examples which refute this!

I think here is some misunderstanding. You suggest that
Escher supports logic programming facilities, Curry does more
and therefore Escher is enough. This point of view is not true
since the Curry approach is not an addition to Escher but an
alternative way to add logic programming facilities to Haskell.
To be a little bit provocative, one could also say that the
approach of Curry is enough ("evaluate functions by simple reduction
steps and instantiate free variables where it is necessary"), so
do we need to go further and add the different rewrite rules
for Booleans? Please note that the entire formal definition of
Curry's operational semantics is only a half page, and this includes
the definition of outermost reduction and the treatment of free
variables. So, the ball can also be in the Escher court to show
realistic examples for Escher that cannot be done in Curry.

Best regards,

Michael
Received on Do Jul 03 1997 - 19:16:00 CEST