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     /** <summary>Do a depth first walk of a tree, applying pre() and post() actions as we go.</summary> */
36     public class TreeVisitor
37     {
38         protected ITreeAdaptor adaptor;
39 
TreeVisitor(ITreeAdaptor adaptor)40         public TreeVisitor(ITreeAdaptor adaptor)
41         {
42             this.adaptor = adaptor;
43         }
TreeVisitor()44         public TreeVisitor()
45             : this(new CommonTreeAdaptor())
46         {
47         }
48 
49         /** <summary>
50          *  Visit every node in tree t and trigger an action for each node
51          *  before/after having visited all of its children.  Bottom up walk.
52          *  Execute both actions even if t has no children.  Ignore return
53          *  results from transforming children since they will have altered
54          *  the child list of this node (their parent).  Return result of
55          *  applying post action to this node.
56          *  </summary>
57          */
Visit(object t, ITreeVisitorAction action)58         public object Visit(object t, ITreeVisitorAction action)
59         {
60             // System.out.println("visit "+((Tree)t).toStringTree());
61             bool isNil = adaptor.IsNil(t);
62             if (action != null && !isNil)
63             {
64                 t = action.Pre(t); // if rewritten, walk children of new t
65             }
66             for (int i = 0; i < adaptor.GetChildCount(t); i++)
67             {
68                 object child = adaptor.GetChild(t, i);
69                 Visit(child, action);
70             }
71             if (action != null && !isNil)
72                 t = action.Post(t);
73             return t;
74         }
75 
Visit(object t, Func<object, object> preAction, Func<object, object> postAction)76         public object Visit(object t, Func<object, object> preAction, Func<object, object> postAction)
77         {
78             return Visit(t, new TreeVisitorAction(preAction, postAction));
79         }
80     }
81 }
82