[gecode-users] "nvalues" global constraint

[Guido Tack]

Jérémie Vautard wrote:
> Is there an implementation of the nvalues global constraint in
> Gecode ? (This constraint is used to specify the number of different
> values in an array of variables, and described in the Global
> constraint catalog here : http://www.emn.fr/x-info/sdemasse/gccat/
> sec5.186.html )

No, we don't have it yet.  You can emulate it using set constraints.  
Here's the pseudo code:

IntVarArgs x;
SetVar y;
IntVar n;
rel(home, SOT_UNION, x, y);
cardinality(home, y, n);

The variable n is now equal to the number of different values in x.   
If the number of values is fixed, you can of course use a constant  
cardinality for y instead.  This decomposition certainly doesn't  
achieve domain consistency, but it should work.

Cheers,
	Guido

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