TernaryConstraint.java
- /* Copyright 2015 Laurent COCAULT
- * Licensed to Laurent COCAULT under one or more contributor license agreements.
- * See the NOTICE file distributed with this work for additional information
- * regarding copyright ownership. Laurent COCAULT licenses this file to You
- * under the Apache License, Version 2.0 (the "License"); you may not use this
- * file except in compliance with the License. You may obtain a copy of the
- * License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- package org.csp.constraint.model;
- /**
- * Represents a ternary constraint in a constraint solving problem To define a
- * new ternary constraint, inherit this class and define the propagate method
- * that must fill the list _recentChangedVariables.
- */
- public abstract class TernaryConstraint<T> extends NAryConstraint<T> {
- /**
- * A ternary constraint is associated with three variables. This attribute
- * is the first variable.
- */
- private Variable<T> firstVariable_;
- /**
- * A ternary constraint is associated with three variables. This attribute
- * is the second variable.
- */
- private Variable<T> secondVariable_;
- /**
- * A ternary constraint is associated with three variables. This attribute
- * is the third variable.
- */
- private Variable<T> thirdVariable_;
- /**
- * Constructor of a ternary constraint. It references three variables given
- * as parameters.
- * @param name
- * Name of the ternary constraint
- * @param first
- * Reference of the first variable
- * @param second
- * Reference of the second variable
- * @param third
- * Reference of the third variable
- */
- public TernaryConstraint(final String name, final Variable<T> first,
- final Variable<T> second, final Variable<T> third) {
- super(name);
- firstVariable_ = first;
- secondVariable_ = second;
- thirdVariable_ = third;
- first.addNAryConstraint(this);
- second.addNAryConstraint(this);
- third.addNAryConstraint(this);
- }
- /**
- * Get the first variable.
- * @return First variable of the constraint
- */
- public Variable<T> getFirstVariable() {
- return firstVariable_;
- }
- /**
- * Get the second variable.
- * @return Second variable of the constraint
- */
- public Variable<T> getSecondVariable() {
- return secondVariable_;
- }
- /**
- * Get the third variable.
- * @return Third variable of the constraint
- */
- public Variable<T> getThirdVariable() {
- return thirdVariable_;
- }
- /**
- * {@inheritDoc}
- */
- @Override
- public boolean isBinary() {
- return false;
- }
- /**
- * {@inheritDoc}
- */
- @Override
- public boolean isTernary() {
- return true;
- }
- /**
- * {@inheritDoc}
- */
- @Override
- public boolean isUnary() {
- return false;
- }
- /**
- * {@inheritDoc}
- */
- @Override
- public boolean isUnsized() {
- return false;
- }
- /**
- * {@inheritDoc}
- */
- @Override
- public boolean isVariableReferenced(final Variable<T> variable) {
- return firstVariable_ == variable || secondVariable_ == variable ||
- thirdVariable_ == variable;
- }
- /**
- * {@inheritDoc}
- */
- @Override
- public boolean revise() {
- try {
- // Initialize the list of reduced variables
- clearRecentChangedVariables();
- if (isPropagationEnabled()) {
- // This list must be updated by the propagation method
- propagate();
- }
- return !firstVariable_.getDomain().isEmpty() &&
- !secondVariable_.getDomain().isEmpty() &&
- !thirdVariable_.getDomain().isEmpty();
- } catch (EmptyDomainException e) {
- // If the domain has been emptied, return false
- return false;
- }
- }
- }