ITreeVisitorAction.cs revision 324c4644fee44b9898524c09511bd33c3f12e2df 
15821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/*
25821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) * [The "BSD licence"]
35821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) * Copyright (c) 2005-2008 Terence Parr
45821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) * All rights reserved.
55821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) *
65821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) * Conversion to C#:
75821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) * Copyright (c) 2008-2009 Sam Harwell, Pixel Mine, Inc.
85821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) * All rights reserved.
95821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) *
105821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) * Redistribution and use in source and binary forms, with or without
115821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) * modification, are permitted provided that the following conditions
125821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) * are met:
135821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) * 1. Redistributions of source code must retain the above copyright
145821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) *    notice, this list of conditions and the following disclaimer.
155821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) * 2. Redistributions in binary form must reproduce the above copyright
165821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) *    notice, this list of conditions and the following disclaimer in the
175821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) *    documentation and/or other materials provided with the distribution.
185821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) * 3. The name of the author may not be used to endorse or promote products
19 *    derived from this software without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
22 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
23 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
24 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
26 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
30 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31 */
32
33namespace Antlr.Runtime.Tree
34{
35    /** <summary>
36     *  How to execute code for node t when a visitor visits node t.  Execute
37     *  pre() before visiting children and execute post() after visiting children.
38     *  </summary>
39     */
40    public interface ITreeVisitorAction
41    {
42        /** <summary>
43         *  Execute an action before visiting children of t.  Return t or
44         *  a rewritten t.  It is up to the visitor to decide what to do
45         *  with the return value.  Children of returned value will be
46         *  visited if using TreeVisitor.visit().
47         *  </summary>
48         */
49        object Pre(object t);
50
51        /** <summary>
52         *  Execute an action after visiting children of t.  Return t or
53         *  a rewritten t.  It is up to the visitor to decide what to do
54         *  with the return value.
55         *  </summary>
56         */
57        object Post(object t);
58    }
59
60    public class TreeVisitorAction
61        : ITreeVisitorAction
62    {
63        Func<object, object> _preAction;
64        Func<object, object> _postAction;
65
66        public TreeVisitorAction(Func<object, object> preAction, Func<object, object> postAction)
67        {
68            _preAction = preAction;
69            _postAction = postAction;
70        }
71
72        public object Pre(object t)
73        {
74            if (_preAction != null)
75                return _preAction(t);
76
77            return t;
78        }
79
80        public object Post(object t)
81        {
82            if (_postAction != null)
83                return _postAction(t);
84
85            return t;
86        }
87    }
88}
89