TreeVisitor.cs revision 324c4644fee44b9898524c09511bd33c3f12e2df 
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
33namespace 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
40        public TreeVisitor(ITreeAdaptor adaptor)
41        {
42            this.adaptor = adaptor;
43        }
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         */
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
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