Re: [eclipse-clp-users] Implication Handling in Eclipse.

From: Kish Shen <kisshen_at_...5...>
Date: Tue, 23 Sep 2008 16:49:45 +0100

There seem to be a problem with my previous reply. I will try again...

I am probably not the best person to answer this, but since you received 
no other replies...

ECLiPSe is a programming platform, with several constraint solver 
libraries. ECLiPSe itself does not `handle' constraints itself. The 
individual solver libraries are the ones that `handle' the constraints.

The paper you cite is about CHR, which is available in ECLiPSe. I have 
not read the paper and do not know the work, but from the summary, it 
appears to be something extra implemented (on top of?) CHR.

The syntax you show is not for CHR, but appears to be a mixture of 
syntax used in two ECLiPSe solvers: ic and the older fd. The constraints 
starting with '#' are fd constraints, while the others like or/2 are ic.
I think the reason for the different syntax is that constraints begining 
with '#' are restricted to integer (finite) domain, while the ic 
versions is not.

In any case, these 'constraints' are reified connectives, and are 
basically a shorthand way for writing several reified constraints, i.e. 
they connect the truth values (and thus if the constraint is posted or 
not) of the constraints in the specified way. As far as I understand it, 
it does not do any extra checking on top of this.



Amine Marref wrote:
> Hi Folks,
> Can anybody direct me to where I can read about how Eclipse handles 
> constraint implication, I browsed the online documentation but was not 
> lucky.
> I am for instance interested in knowing whether the following two 
> clauses have an equivalent behavior in ECLIPSE.
> solve1(G):- c1(G) #=> c2(G).
> solve2(G):- (#\+ c1(G)) or c2(G).
> Is constraint implication checked like discussed in [1]?
> Regards,
> Amine.
> [1] Automatic Implication Checking for CHR Constraints by Tom Schrijvers 
> A, Peter Stuckey B, C Thom Frühwirth D, 

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Received on Tue Sep 23 2008 - 16:19:32 CEST

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