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/*
 * 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; } }




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