Re: external solvers

From: Michael Hanus <>
Date: Tue, 04 Jan 2005 14:06:25 +0100

Igor wrote:
> Is there any detailed documentation on concept of "external constraint solvers"
> and their implementation? It seems that I do not really understand
> how this is supposed to work and what this is supposed to do.
> I supposed that external solvers are intended to solve constraints
> that language core is unable to solve. But if this is true, I do not
> understand how it can be done through external solver API defined.

Section 9.2 of the Curry report is not really considered as an API
for external solvers. It should only give a hint which kind of
operations a constraint solver must provide in order to be compatible
with Curry's computation model. This section was written at a very
early stage and has not been touched since then. It might be
necessary to refine it in the light of later developments
(in particular, sharing and encapsulated search).

Current implementations of Curry, like PAKCS or MCC, provide
particular constraints as standard (external) functions.
For instance, PAKCS provides two modules CLPR and CLPFD
supporting real arithmetic and finite domain constraints,
respectively. Thus, as a programmer, you only have to look at the
interface of these modules (see and
The actual connection of constraint solvers to a Curry implementation
could be quite subtle and might need more details than described
in the Curry report.

Best regards,


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Received on Di Jan 04 2005 - 14:35:14 CET

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