org.chocosolver.solver.constraints.unary.PropNotEqualXC Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of choco-solver Show documentation
Show all versions of choco-solver Show documentation
Open-source constraint solver.
/*
* This file is part of choco-solver, http://choco-solver.org/
*
* Copyright (c) 2019, IMT Atlantique. All rights reserved.
*
* Licensed under the BSD 4-clause license.
*
* See LICENSE file in the project root for full license information.
*/
package org.chocosolver.solver.constraints.unary;
import org.chocosolver.solver.constraints.Propagator;
import org.chocosolver.solver.constraints.PropagatorPriority;
import org.chocosolver.solver.exception.ContradictionException;
import org.chocosolver.solver.learn.ExplanationForSignedClause;
import org.chocosolver.solver.learn.Implications;
import org.chocosolver.solver.variables.IntVar;
import org.chocosolver.util.ESat;
import org.chocosolver.util.objects.ValueSortedMap;
import org.chocosolver.util.objects.setDataStructures.iterable.IntIterableRangeSet;
/**
* A propagator ensuring that:
* X =/= C, where X is a variable and C a constant
*
*
* @author Charles Prud'homme
* @since 16/06/11
*/
public class PropNotEqualXC extends Propagator {
private final int constant;
public PropNotEqualXC(IntVar var, int cste) {
super(new IntVar[]{var}, PropagatorPriority.UNARY, false, true);
this.constant = cste;
}
@Override
public void propagate(int evtmask) throws ContradictionException {
if (vars[0].removeValue(constant, this) || !vars[0].contains(constant)) {
this.setPassive();
}
}
@Override
public ESat isEntailed() {
if (vars[0].isInstantiatedTo(constant)) {
return ESat.FALSE;
} else if (vars[0].contains(constant)) {
return ESat.UNDEFINED;
}
return ESat.TRUE;
}
/**
* @implSpec
*
* Consider that v1 has been modified by propagation of this.
* Before the propagation, the domains were like:
*
* (v1 ∈ D1)
*
* Then this propagates v1 ≠ c, then:
*
* (v1 ∈ D1) → v1 ≠ c
*
* Converting to DNF:
*
* (v1 ∈ (U \ D1) ∪ (U \ c))
*
*
*/
@Override
public void explain(ExplanationForSignedClause explanation,
ValueSortedMap front,
Implications ig, int p) {
IntIterableRangeSet set = explanation.getRootSet(vars[0]);
set.remove(constant);
explanation.addLiteral(vars[0], set, true);
}
@Override
public String toString() {
return vars[0].getName() + " =/= " + constant;
}
}