[gecode-users] catalog (compatibility) constraints in Gecode

[Guido Tack]

Hi!

Nicolas BERGER wrote:
> Are catalog (compatibility) constraints such as (x,y,z) \in
> {(1,2,3),(4,4,4),(8,6,9)} allowed in Gecode ? How to represent them ?

In the released version of Gecode (1.3.1), we don't have a special  
propagator for this kind of constraint. You can, however, express  
them using the regular constraint. Your example would look like this:

REG reg = (REG(1)+REG(2)+REG(3)) | (REG(4)+REG(4)+REG(4)) | (REG(8) 
+REG(6)+REG(9));
DFA dfa = reg;
IntVarArgs xs(3);
xs[0] = x; xs[1] = y; xs[2] = z;
regular(this, xs, dfa);

However, the resulting DFAs may become big, so this may not be a good  
solution for all applications. The next version of Gecode will come  
with a specialized propagator for this constraint.

Cheers,
	Guido

-- 
Guido Tack
Programming Systems Lab, Saarland University, Germany
http://www.ps.uni-sb.de/~tack



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