    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 * @author  Tomáš Müller
    021 * @version IFS 1.3 (Iterative Forward Search)<br>
    022 *          Copyright (C) 2006 - 2014 Tomáš Müller<br>
    023 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
    024 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
    025 * <br>
    026 *          This library is free software; you can redistribute it and/or modify
    027 *          it under the terms of the GNU Lesser General Public License as
    028 *          published by the Free Software Foundation; either version 3 of the
    029 *          License, or (at your option) any later version. <br>
    030 * <br>
    031 *          This library is distributed in the hope that it will be useful, but
    032 *          WITHOUT ANY WARRANTY; without even the implied warranty of
    033 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    034 *          Lesser General Public License for more details. <br>
    035 * <br>
    036 *          You should have received a copy of the GNU Lesser General Public
    037 *          License along with this library; if not see
    038 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
    039 * @param <V> Variable
    040 * @param <T> Value
    041 */
    042public abstract class GlobalConstraint<V extends Variable<V, T>, T extends Value<V, T>> extends Constraint<V, T> {
    043
    044    /** The list of variables of this constraint */
    045    @Override
    046    public List<V> variables() {
    047        return getModel().variables();
    048    }
    049
    050    /** The list of variables of this constraint that are assigned */
    051    @Override
    052    public Collection<V> assignedVariables(Assignment<V, T> assignment) {
    053        return assignment.assignedVariables();
    054    }
    055
    056    /** The number of variables of this constraint that are assigned */
    057    @Override
    058    public int countAssignedVariables(Assignment<V, T> assignment) {
    059        return assignment.nrAssignedVariables();
    060    }
    061
    062    /** Add a variable to this constraint */
    063    @Override
    064    public void addVariable(V variable) {
    065        throw new RuntimeException("A variable cannot be added to a global constraint.");
    066    }
    067
    068    /** Remove a variable from this constraint */
    069    @Override
    070    public void removeVariable(V variable) {
    071        throw new RuntimeException("A variable cannot be removed from a global constraint.");
    072    }
    073
    074    /**
    075     * Given value is to be assigned to its variable. In this method, the
    076     * constraint should unassigns all variables which are in conflict with the
    077     * given assignment because of this constraint.
    078     */
    079    @Override
    080    public void assigned(Assignment<V, T> assignment, long iteration, T value) {
    081        HashSet<T> conf = null;
    082        if (isHard()) {
    083            conf = new HashSet<T>();
    084            computeConflicts(assignment, value, conf);
    085        }
    086        if (constraintListeners() != null)
    087            for (ConstraintListener<V, T> listener : iConstraintListeners)
    088                listener.constraintBeforeAssigned(assignment, iteration, this, value, conf);
    089        if (conf != null) {
    090            for (T conflictValue : conf) {
    091                if (!conflictValue.equals(value))
    092                   assignment.unassign(iteration, conflictValue.variable());
    093            }
    094        }
    095        if (constraintListeners() != null)
    096            for (ConstraintListener<V, T> listener : iConstraintListeners)
    097                listener.constraintAfterAssigned(assignment, iteration, this, value, conf);
    098    }
    099
    100    /**
    101     * Given value is unassigned from its varable.
    102     */
    103    @Override
    104    public void unassigned(Assignment<V, T> assignment, long iteration, T value) {
    105    }
    106}