On Thu, 6 Apr 2006, Claus Reinke wrote:
Curry does not have a constraint solver of its own. It simply delegates all
constraints to the FD solver of SICStus Prolog.
or that of SWI Prolog (which prompted my attempt to install Curry).
which was implemented by.. hi, again!-) (*)
The SWI-Prolog FD library is just a prototype implementation... looking
for someone to replace it with a state-of-the-art implementation.
The all_different constraint subsumes the rules that you describe,
depending on the consistency algorithm used. FD solvers implement general
but efficient algorithms that are much more complex than a few simple
rules.
I haven't yet been able to get Curry to work on my windows machine,
but it seems to do a straightforward translation of these constraints to
Prolog > +FD solver, close to the one I've attached (an easy way to "use" external
constraint solvers from Haskell;-).
:)
the docs you pointed to state that all_different, in declarative view, simply
translates into mutual inequalities between the list members, and although I
don't fully understand the sources, they seem to confirm that not much more
is going on.
The SWI-Prolog prototype library does nothing more than the declarative
meaning, that's why it's a prototype.
State-of-the-art all_different implementations are a lot more complicated
(often based on graph algorithms) to do very strong propagation.
Here is a paper about solving Sudoku with constraint (logic )
programming comparing a number of all_different algorithms and additional
tricks:
http://www.computational-logic.org/iccl/master/lectures/winter05/fcp/fcp/sudoku.pdf
Cheers,
Tom
--
Tom Schrijvers
Department of Computer Science
K.U. Leuven
Celestijnenlaan 200A
B-3001 Heverlee
Belgium
tel: +32 16 327544
e-mail: [EMAIL PROTECTED]
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