001/*
002 * Copyright (C) 2009-2011 Mathias Doenitz
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.parboiled.trees;
018
019/**
020 * A specialization of a {@link GraphNode} that contains a reference to its parent, thereby making the graph a tree
021 * (since each node can now have only one parent node).
022 *
023 * @param <T> the actual implementation type of this TreeNode
024 */
025public interface TreeNode<T extends TreeNode<T>> extends GraphNode<T> {
026
027    /**
028     * Returns the parent node or null if this node is the root.
029     *
030     * @return the parent node
031     */
032    T getParent();
033
034}