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      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>
     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