001/* Copyright (C) 2013 TU Dortmund
002 * This file is part of AutomataLib, http://www.automatalib.net/.
003 * 
004 * AutomataLib is free software; you can redistribute it and/or
005 * modify it under the terms of the GNU Lesser General Public
006 * License version 3.0 as published by the Free Software Foundation.
007 * 
008 * AutomataLib is distributed in the hope that it will be useful,
009 * but WITHOUT ANY WARRANTY; without even the implied warranty of
010 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
011 * Lesser General Public License for more details.
012 * 
013 * You should have received a copy of the GNU Lesser General Public
014 * License along with AutomataLib; if not, see
015 * http://www.gnu.de/documents/lgpl.en.html.
016 */
017package net.automatalib.util.traversal;
018
019/**
020 * Enum to use for indicating if a node/state has been visited.
021 * <p>
022 * Note that this enum only declares one value. The value {@link #NOT_VISITED} for unvisited
023 * nodes/states is identified with <tt>null</tt>.
024 * 
025 * @author Malte Isberner <malte.isberner@gmail.com>
026 *
027 */
028public enum VisitedState {
029        /**
030         * Nodes that have already been visited.
031         */
032        VISITED;
033        
034        /**
035         * Nodes that have not yet been visited.
036         */
037        public static final VisitedState NOT_VISITED = null;
038}