001 package net.sf.cpsolver.ifs.model;
002
003 import java.util.Enumeration;
004 import java.util.HashSet;
005 import java.util.Iterator;
006 import java.util.Vector;
007
008 import net.sf.cpsolver.ifs.util.EnumerableCollection;
009
010 /**
011 * Generic global constraint.
012 * <br><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 net.sf.cpsolver.ifs.solver.Solver
019 *
020 * @version
021 * IFS 1.1 (Iterative Forward Search)<br>
022 * Copyright (C) 2006 Tomáš Müller<br>
023 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
024 * Lazenska 391, 76314 Zlin, Czech Republic<br>
025 * <br>
026 * This library is free software; you can redistribute it and/or
027 * modify it under the terms of the GNU Lesser General Public
028 * License as published by the Free Software Foundation; either
029 * version 2.1 of the License, or (at your option) any later version.
030 * <br><br>
031 * This library is distributed in the hope that it will be useful,
032 * but 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.
035 * <br><br>
036 * You should have received a copy of the GNU Lesser General Public
037 * License along with this library; if not, write to the Free Software
038 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
039 */
040
041 public abstract class GlobalConstraint extends Constraint {
042
043 /** The list of variables of this constraint */
044 public Vector variables() { return getModel().variables(); }
045 /** The list of variables of this constraint that are assigned */
046 public EnumerableCollection assignedVariables() { return getModel().assignedVariables(); }
047
048 /** Add a variable to this constraint */
049 public void addVariable(Variable variable) {
050 throw new RuntimeException("A variable cannot be added to a global constraint.");
051 }
052 /** Remove a variable from this constraint */
053 public void removeVariable(Variable variable) {
054 throw new RuntimeException("A variable cannot be removed from a global constraint.");
055 }
056
057 /** Given value is to be assigned to its varable. In this method, the constraint should unassigns
058 * all varaibles which are in conflict with the given assignment because of this constraint.
059 */
060 public void assigned(long iteration, Value value) {
061 HashSet conf = null;
062 if (isHard()) {
063 conf = new HashSet(); computeConflicts(value, conf);
064 }
065 if (constraintListeners()!=null)
066 for (Enumeration e=constraintListeners().elements();e.hasMoreElements();)
067 ((ConstraintListener)e.nextElement()).constraintBeforeAssigned(iteration, this, value, conf);
068 if (conf!=null) {
069 for (Iterator i=conf.iterator(); i.hasNext(); ) {
070 Value conflictValue = (Value)i.next();
071 conflictValue.variable().unassign(iteration);
072 }
073 }
074 if (constraintListeners()!=null)
075 for (Enumeration e=constraintListeners().elements();e.hasMoreElements();)
076 ((ConstraintListener)e.nextElement()).constraintAfterAssigned(iteration, this, value, conf);
077 }
078
079 /** Given value is unassigned from its varable.
080 */
081 public void unassigned(long iteration, Value value) {
082 }
083 }