    001package org.cpsolver.ifs.model;
    002
    003import java.util.Collection;
    004import java.util.HashSet;
    005import java.util.List;
    006
    007import org.cpsolver.ifs.assignment.Assignment;
    008
    009
    010/**
    011 * Generic global constraint. <br>
    012 * <br>
    013 * Global constraint is a {@link Constraint} that applies to all variables.
    014 *
    015 * @see Variable
    016 * @see Model
    017 * @see Constraint
    018 * @see org.cpsolver.ifs.solver.Solver
    019 *
    020 * @version IFS 1.3 (Iterative Forward Search)<br>
    021 *          Copyright (C) 2006 - 2014 Tomáš Müller<br>
    022 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    023 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    024 * <br>
    025 *          This library is free software; you can redistribute it and/or modify
    026 *          it under the terms of the GNU Lesser General Public License as
    027 *          published by the Free Software Foundation; either version 3 of the
    028 *          License, or (at your option) any later version. <br>
    029 * <br>
    030 *          This library is distributed in the hope that it will be useful, but
    031 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    032 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    033 *          Lesser General Public License for more details. <br>
    034 * <br>
    035 *          You should have received a copy of the GNU Lesser General Public
    036 *          License along with this library; if not see
    037 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    038 * @param <V> Variable
    039 * @param <T> Value
    040 */
    041public abstract class GlobalConstraint<V extends Variable<V, T>, T extends Value<V, T>> extends Constraint<V, T> {
    042
    043    /** The list of variables of this constraint */
    044    @Override
    045    public List<V> variables() {
    046        return getModel().variables();
    047    }
    048
    049    /** The list of variables of this constraint that are assigned */
    050    @Override
    051    public Collection<V> assignedVariables(Assignment<V, T> assignment) {
    052        return assignment.assignedVariables();
    053    }
    054
    055    /** The number of variables of this constraint that are assigned */
    056    @Override
    057    public int countAssignedVariables(Assignment<V, T> assignment) {
    058        return assignment.nrAssignedVariables();
    059    }
    060
    061    /** Add a variable to this constraint */
    062    @Override
    063    public void addVariable(V variable) {
    064        throw new RuntimeException("A variable cannot be added to a global constraint.");
    065    }
    066
    067    /** Remove a variable from this constraint */
    068    @Override
    069    public void removeVariable(V variable) {
    070        throw new RuntimeException("A variable cannot be removed from a global constraint.");
    071    }
    072
    073    /**
    074     * Given value is to be assigned to its variable. In this method, the
    075     * constraint should unassigns all variables which are in conflict with the
    076     * given assignment because of this constraint.
    077     */
    078    @Override
    079    public void assigned(Assignment<V, T> assignment, long iteration, T value) {
    080        HashSet<T> conf = null;
    081        if (isHard()) {
    082            conf = new HashSet<T>();
    083            computeConflicts(assignment, value, conf);
    084        }
    085        if (constraintListeners() != null)
    086            for (ConstraintListener<V, T> listener : iConstraintListeners)
    087                listener.constraintBeforeAssigned(assignment, iteration, this, value, conf);
    088        if (conf != null) {
    089            for (T conflictValue : conf) {
    090                if (!conflictValue.equals(value))
    091                   assignment.unassign(iteration, conflictValue.variable());
    092            }
    093        }
    094        if (constraintListeners() != null)
    095            for (ConstraintListener<V, T> listener : iConstraintListeners)
    096                listener.constraintAfterAssigned(assignment, iteration, this, value, conf);
    097    }
    098
    099    /**
    100     * Given value is unassigned from its varable.
    101     */
    102    @Override
    103    public void unassigned(Assignment<V, T> assignment, long iteration, T value) {
    104    }
    105}