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Open-source constraint solver.
/**
* Copyright (c) 2016, Ecole des Mines de Nantes
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the .
* 4. Neither the name of the nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY ''AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.chocosolver.solver.constraints.reification;
import org.chocosolver.solver.constraints.Propagator;
import org.chocosolver.solver.constraints.PropagatorPriority;
import org.chocosolver.solver.exception.ContradictionException;
import org.chocosolver.solver.explanations.RuleStore;
import org.chocosolver.solver.variables.BoolVar;
import org.chocosolver.solver.variables.IntVar;
import org.chocosolver.solver.variables.events.IEventType;
import org.chocosolver.util.ESat;
/**
* A propagator dedicated to express in a compact way: (x = y) ⇔ b
*
* @author Charles Prud'homme
* @since 03/05/2016.
*/
public class PropXeqYReif extends Propagator {
public PropXeqYReif(IntVar x, IntVar y, BoolVar r) {
super(new IntVar[]{x, y, r}, PropagatorPriority.TERNARY, false);
}
@Override
public void propagate(int evtmask) throws ContradictionException {
if (vars[2].getLB() == 1) {
if (vars[0].isInstantiated()) {
setPassive();
vars[1].instantiateTo(vars[0].getValue(), this);
} else if (vars[1].isInstantiated()) {
setPassive();
vars[0].instantiateTo(vars[1].getValue(), this);
}
} else if (vars[2].getUB() == 0) {
if (vars[0].isInstantiated()) {
if (vars[1].removeValue(vars[0].getValue(), this) || !vars[1].contains(vars[0].getValue())) {
setPassive();
}
} else if (vars[1].isInstantiated()) {
if (vars[0].removeValue(vars[1].getValue(), this) || !vars[0].contains(vars[1].getValue())) {
setPassive();
}
}
} else {
if (vars[0].isInstantiated()) {
if (vars[1].isInstantiated()) {
setPassive();
if (vars[0].getValue() == vars[1].getValue()) {
vars[2].instantiateTo(1, this);
} else {
vars[2].instantiateTo(0, this);
}
} else if (!vars[1].contains(vars[0].getValue())) {
setPassive();
vars[2].instantiateTo(0, this);
}
} else {
if (vars[1].isInstantiated()) {
if (!vars[0].contains(vars[1].getValue())) {
setPassive();
vars[2].instantiateTo(0, this);
}
} else {
if (vars[0].getLB() > vars[1].getUB()
|| vars[1].getLB() > vars[0].getUB()) {
setPassive();
vars[2].instantiateTo(0, this);
}
}
}
}
}
@Override
public ESat isEntailed() {
if(isCompletelyInstantiated()){
if(vars[2].isInstantiatedTo(1)){
return ESat.eval(vars[0].getValue() == vars[1].getValue());
}else{
return ESat.eval(vars[0].getValue() != vars[1].getValue());
}
}
return ESat.UNDEFINED;
}
@Override
public boolean why(RuleStore ruleStore, IntVar var, IEventType evt, int value) {
boolean nrules = ruleStore.addPropagatorActivationRule(this);
if (var == vars[2]) {
if (vars[2].isInstantiatedTo(1)) {
nrules |= ruleStore.addFullDomainRule(vars[0]);
nrules |= ruleStore.addFullDomainRule(vars[1]);
} else {
if (vars[0].isInstantiated()) {
nrules |= ruleStore.addRemovalRule(vars[1], vars[0].getValue());
} else {
nrules |= ruleStore.addFullDomainRule(vars[1]);
}
if (vars[1].isInstantiated()) {
nrules |= ruleStore.addRemovalRule(vars[0], vars[1].getValue());
} else {
nrules |= ruleStore.addFullDomainRule(vars[0]);
}
}
} else {
if (var == vars[0]) {
nrules |= ruleStore.addFullDomainRule(vars[1]);
} else if (var == vars[1]) {
nrules |= ruleStore.addFullDomainRule(vars[0]);
}
nrules |= ruleStore.addFullDomainRule(vars[2]);
}
return nrules;
}
@Override
public String toString() {
return "(" + vars[0].getName() +" = " + vars[0].getName() + ") <=> "+vars[2].getName();
}
}