001/*
002 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved.
003 *
004 * Project and contact information: http://www.cascading.org/
005 *
006 * This file is part of the Cascading project.
007 *
008 * Licensed under the Apache License, Version 2.0 (the "License");
009 * you may not use this file except in compliance with the License.
010 * You may obtain a copy of the License at
011 *
012 *     http://www.apache.org/licenses/LICENSE-2.0
013 *
014 * Unless required by applicable law or agreed to in writing, software
015 * distributed under the License is distributed on an "AS IS" BASIS,
016 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
017 * See the License for the specific language governing permissions and
018 * limitations under the License.
019 */
020
021package cascading.flow.planner.graph;
022
023import cascading.flow.FlowElement;
024
025/**
026 * Enum Extent provides simple markers for the head and tail of an {@link ElementGraph} {@link FlowElement} graph.
027 */
028public enum Extent implements FlowElement
029  {
030    head,
031    tail;
032
033  @Override
034  public String toString()
035    {
036    return "[" + name() + "]";
037    }
038  }