1 /*
2  * [The "BSD licence"]
3  * Copyright (c) 2005-2008 Terence Parr
4  * All rights reserved.
5  *
6  * Conversion to C#:
7  * Copyright (c) 2008-2009 Sam Harwell, Pixel Mine, Inc.
8  * All rights reserved.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  * 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 
33 namespace Antlr.Runtime.Tree
34 {
35     using Antlr.Runtime.Misc;
36 
37     /** <summary>
38      *  How to execute code for node t when a visitor visits node t.  Execute
39      *  pre() before visiting children and execute post() after visiting children.
40      *  </summary>
41      */
42     public interface ITreeVisitorAction
43     {
44         /** <summary>
45          *  Execute an action before visiting children of t.  Return t or
46          *  a rewritten t.  It is up to the visitor to decide what to do
47          *  with the return value.  Children of returned value will be
48          *  visited if using TreeVisitor.visit().
49          *  </summary>
50          */
Pre( object t )51         object Pre( object t );
52 
53         /** <summary>
54          *  Execute an action after visiting children of t.  Return t or
55          *  a rewritten t.  It is up to the visitor to decide what to do
56          *  with the return value.
57          *  </summary>
58          */
Post( object t )59         object Post( object t );
60     }
61 
62     public class TreeVisitorAction
63         : ITreeVisitorAction
64     {
65         private readonly Func<object, object> _preAction;
66         private readonly Func<object, object> _postAction;
67 
TreeVisitorAction( Func<object, object> preAction, Func<object, object> postAction )68         public TreeVisitorAction( Func<object, object> preAction, Func<object, object> postAction )
69         {
70             _preAction = preAction;
71             _postAction = postAction;
72         }
73 
Pre( object t )74         public object Pre( object t )
75         {
76             if ( _preAction != null )
77                 return _preAction( t );
78 
79             return t;
80         }
81 
Post( object t )82         public object Post( object t )
83         {
84             if ( _postAction != null )
85                 return _postAction( t );
86 
87             return t;
88         }
89     }
90 }
91