001package org.cpsolver.ifs.constant;
002
003import org.cpsolver.ifs.model.Value;
004
005/**
006 * Extension of a variable with the possibility to have a constant value.
007 * 
008 * Such variables are excluded from the solver process, however, they can be
009 * included in constraints.
010 * 
011 * @author  Tomáš Müller
012 * @version IFS 1.3 (Iterative Forward Search)<br>
013 *          Copyright (C) 2006 - 2014 Tomáš Müller<br>
014 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
015 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
016 * <br>
017 *          This library is free software; you can redistribute it and/or modify
018 *          it under the terms of the GNU Lesser General Public License as
019 *          published by the Free Software Foundation; either version 3 of the
020 *          License, or (at your option) any later version. <br>
021 * <br>
022 *          This library is distributed in the hope that it will be useful, but
023 *          WITHOUT ANY WARRANTY; without even the implied warranty of
024 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
025 *          Lesser General Public License for more details. <br>
026 * <br>
027 *          You should have received a copy of the GNU Lesser General Public
028 *          License along with this library; if not see <a href='http://www.gnu.org/licenses'>http://www.gnu.org/licenses</a>.
029 * 
030 * @param <T> Value
031 */
032public interface ConstantVariable<T extends Value<?, T>> {
033    /** True, if the variable is constant. 
034     * @return true if constant
035     **/
036    public boolean isConstant();
037    
038    /** Return assignment if constant
039     * @return constant value (if {@link ConstantVariable#isConstant()} is true)
040     **/
041    public T getConstantValue();
042}