    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}