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