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Open-source constraint solver.
/*
* This file is part of choco-solver, http://choco-solver.org/
*
* Copyright (c) 2022, 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.variables.view.bool;
import org.chocosolver.solver.ICause;
import org.chocosolver.solver.exception.ContradictionException;
import org.chocosolver.solver.learn.ExplanationForSignedClause;
import org.chocosolver.solver.variables.IntVar;
import org.chocosolver.solver.variables.events.IntEventType;
import org.chocosolver.solver.variables.view.BoolIntView;
import org.chocosolver.util.ESat;
import org.chocosolver.util.objects.setDataStructures.iterable.IntIterableRangeSet;
/**
* declare an BoolVar based on X and C, such as (X = C) is reified by this.
Based on "Views
* and Iterators for Generic Constraint Implementations"
C. Shulte and G. Tack.
Eleventh
* International Conference on Principles and Practice of Constraint Programming
*
* @author Charles Prud'homme
* @since 04/02/11
*/
public final class BoolEqView extends BoolIntView {
/**
* A boolean view based on var such that var = cste
*
* @param var an integer variable
* @param cste an int
*/
public BoolEqView(final I var, final int cste) {
super(var, "=", cste);
}
@Override
public ESat getBooleanValue() {
if (var.isInstantiated()) {
return var.getValue() == cste ? ESat.TRUE : ESat.FALSE;
} else if (var.contains(cste)) {
return ESat.UNDEFINED;
}
return ESat.FALSE;
}
@Override
public boolean instantiateTo(int value, ICause cause) throws ContradictionException {
assert cause != null;
boolean done = false;
if (!this.contains(value)) {
model.getSolver().getEventObserver().instantiateTo(this, value, cause, getLB(), getUB());
this.contradiction(cause, MSG_EMPTY);
} else if (!isInstantiated()) {
model.getSolver().getEventObserver().instantiateTo(this, value, cause, getLB(), getUB());
this.fixed.set(true);
if (reactOnRemoval) {
delta.add(1 - value, cause);
}
if (value == 1) {
done = var.instantiateTo(cste, this);
} else {
done = var.removeValue(cste, this);
}
notifyPropagators(IntEventType.INSTANTIATE, cause);
}
return done;
}
@Override
public int getDomainSize() {
return isInstantiated()?1:2;
}
@Override
public boolean isInstantiated() {
if (var.isInstantiated()) {
return true;
} else return !var.contains(cste);
}
@Override
public boolean contains(int value) {
if (value == 0) {
return !var.isInstantiatedTo(cste);
} else if (value == 1) {
return var.contains(cste);
}
return false;
}
@Override
public boolean isInstantiatedTo(int value) {
if (value == 0) {
return !var.contains(cste);
} else if (value == 1) {
return var.isInstantiatedTo(cste);
}
return false;
}
@Override
public int getLB() {
if (var.isInstantiatedTo(cste)) {
return 1;
}
return 0;
}
@Override
public int getUB() {
if (!var.contains(cste)) {
return 0;
}
return 1;
}
@Override
public int nextValue(int v) {
if (v < 0 && contains(0)) {
return 0;
}
return v <= 0 && contains(1) ? 1 : Integer.MAX_VALUE;
}
@Override
public int nextValueOut(int v) {
int lb = 0, ub = 1;
if (!var.contains(cste)) {
ub = 0;
} else if (var.isInstantiated()) {
lb = 1;
}
if (lb - 1 <= v && v <= ub) {
return ub + 1;
} else {
return v + 1;
}
}
@Override
public int previousValue(int v) {
if (v > 1 && contains(1)) {
return 1;
}
return v >= 1 && contains(0) ? 0 : Integer.MIN_VALUE;
}
@Override
public int previousValueOut(int v) {
int lb = 0, ub = 1;
if (!var.contains(cste)) {
ub = 0;
} else if (var.isInstantiated()) {
lb = 1;
}
if (lb <= v && v <= ub + 1) {
return lb - 1;
} else {
return v - 1;
}
}
@Override
public void justifyEvent(IntEventType mask, int one, int two, int three) {
if (this.isInstantiated()) return;
switch (mask) {
case DECUPP:
if (one < cste) {
model.getSolver().getEventObserver().instantiateTo(this, 0, this, 0, 1);
} else if (this.var.getLB() == cste && (one == cste || this.var.previousValue(one + 1) == cste)) {
model.getSolver().getEventObserver().instantiateTo(this, 1, this, 0, 1);
}
break;
case INCLOW:
if (cste < one) {
model.getSolver().getEventObserver().instantiateTo(this, 0, this, 0, 1);
} else if (this.var.getUB() == cste && (one == cste || this.var.nextValue(one - 1) == cste)) {
model.getSolver().getEventObserver().instantiateTo(this, 1, this, 0, 1);
}
break;
case REMOVE:
if (one == cste) {
model.getSolver().getEventObserver().instantiateTo(this, 0, this, 0, 1);
} else if (this.var.getDomainSize() == 2 && this.var.contains(cste)) {
model.getSolver().getEventObserver().instantiateTo(this, 1, this, 0, 1);
}
break;
case INSTANTIATE:
if (one == cste) {
model.getSolver().getEventObserver().instantiateTo(this, 1, this, 0, 1);
} else {
model.getSolver().getEventObserver().instantiateTo(this, 0, this, 0, 1);
}
break;
}
}
@Override
public void explain(int p, ExplanationForSignedClause explanation) {
IntVar pivot = explanation.readVar(p);
int value = getValue();
if (value == 1) { // b is true and X = c holds
if (pivot == this) { // b is the pivot
this.intersectLit(1, explanation);
IntIterableRangeSet dom0 = explanation.universe();
dom0.remove(cste);
var.unionLit(dom0, explanation);
} else if (pivot == var) { // x is the pivot
this.unionLit(0, explanation);
var.intersectLit(cste, explanation);
}
} else if (value == 0) {
if (pivot == this) { // b is the pivot
this.intersectLit(0, explanation);
var.unionLit(cste, explanation);
} else if (pivot == var) { // x is the pivot, case e. in javadoc
this.unionLit(1, explanation);
IntIterableRangeSet dom0 = explanation.universe();
dom0.remove(cste);
var.intersectLit(dom0, explanation);
}
}
}
}