Re: [eclipse-clp-users] Constraints in Loop

From: Kish Shen <kisshen_at_...5...>
Date: Thu, 29 Oct 2009 18:15:16 +0000
Igor Kondrasovas wrote:
>       (for(I,1,NPieces) do
>             M[I,1] + M[I,2] + M[I,3] #= 1),

Your problem is a common error with using the do loops, which is an 
ECLiPSe extension to Prolog. The scope rule for variables inside do 
loops is perhaps unusual: the scope does not extend into the body of a 
do loop, so the M inside the loop is different from the M outside. You 
need to pass M in as a parameter:

     (for(I,1,NPieces), param(M) do

The reason you don't get an error when you use =/2 instead of #=/2 is
not because the correct variable is accessed, but simply because you are 
performing a simple unification, which is fine with the uninstantiated 
variable M inside the loop -- it is still not the same M as outside. (In 
your specific case, the unification should be failing, because the two 
sides of the = will not unify).


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Received on Thu Oct 29 2009 - 18:15:42 CET

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