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1   /*
2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/BooleanFunction.java,v 1.10 2005/01/14 02:52:17 elharo Exp $
3    * $Revision: 1.10 $
4    * $Date: 2005/01/14 02:52:17 $
5    *
6    * ====================================================================
7    *
8    * Copyright (C) 2000-2002 bob mcwhirter & James Strachan.
9    * All rights reserved.
10   *
11   * Redistribution and use in source and binary forms, with or without
12   * modification, are permitted provided that the following conditions
13   * are met:
14   * 
15   * 1. Redistributions of source code must retain the above copyright
16   *    notice, this list of conditions, and the following disclaimer.
17   *
18   * 2. Redistributions in binary form must reproduce the above copyright
19   *    notice, this list of conditions, and the disclaimer that follows 
20   *    these conditions in the documentation and/or other materials 
21   *    provided with the distribution.
22   *
23   * 3. The name "Jaxen" must not be used to endorse or promote products
24   *    derived from this software without prior written permission.  For
25   *    written permission, please contact license@jaxen.org.
26   * 
27   * 4. Products derived from this software may not be called "Jaxen", nor
28   *    may "Jaxen" appear in their name, without prior written permission
29   *    from the Jaxen Project Management (pm@jaxen.org).
30   * 
31   * In addition, we request (but do not require) that you include in the 
32   * end-user documentation provided with the redistribution and/or in the 
33   * software itself an acknowledgement equivalent to the following:
34   *     "This product includes software developed by the
35   *      Jaxen Project (http://www.jaxen.org/)."
36   * Alternatively, the acknowledgment may be graphical using the logos 
37   * available at http://www.jaxen.org/
38   *
39   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
40   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
41   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
42   * DISCLAIMED.  IN NO EVENT SHALL THE Jaxen AUTHORS OR THE PROJECT
43   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
44   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
45   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
46   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
47   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
48   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
49   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50   * SUCH DAMAGE.
51   *
52   * ====================================================================
53   * This software consists of voluntary contributions made by many 
54   * individuals on behalf of the Jaxen Project and was originally 
55   * created by bob mcwhirter <bob@werken.com> and 
56   * James Strachan <jstrachan@apache.org>.  For more information on the 
57   * Jaxen Project, please see <http://www.jaxen.org/>.
58   * 
59   * $Id: BooleanFunction.java,v 1.10 2005/01/14 02:52:17 elharo Exp $
60   */
61  
62  
63  package org.jaxen.function;
64  
65  import java.util.List;
66  
67  import org.jaxen.Context;
68  import org.jaxen.Function;
69  import org.jaxen.FunctionCallException;
70  import org.jaxen.Navigator;
71  
72  /***
73   *  <p><b>4.3</b> <code><i>boolean</i> boolean(<i>object</i>)</code> 
74   *  
75   *  @author bob mcwhirter (bob @ werken.com)
76   */
77  public class BooleanFunction implements Function
78  {
79  
80      public Object call(Context context,
81                         List args) throws FunctionCallException
82      {
83          if ( args.size() == 1 )
84          {
85              return evaluate( args.get(0), context.getNavigator() );
86          }
87  
88          throw new FunctionCallException("boolean() requires one argument");
89      }
90  
91      public static Boolean evaluate(Object obj, Navigator nav)
92      {
93          if ( obj instanceof List )
94          {
95              List list = (List) obj;
96              
97              // if it's an empty list, then we have a null node-set -> false            
98              if (list.size() == 0)
99              {
100                 return Boolean.FALSE;
101             }
102      
103             // otherwise, unwrap the list and check the primitive
104             obj = list.get(0);
105         }
106         
107         // now check for primitive types
108         // otherwise a non-empty node-set is true
109 
110         // if it's a Boolean, let it decide
111         if ( obj instanceof Boolean )
112         {
113             return (Boolean) obj;
114         }
115         // if it's a Number, != 0 -> true
116         else if ( obj instanceof Number )
117         {
118             double d = ((Number) obj).doubleValue();
119             if ( d == 0 || Double.isNaN(d) )
120             {
121                 return Boolean.FALSE;
122             }
123             return Boolean.TRUE;
124         }
125         // if it's a String, "" -> false
126         else if ( obj instanceof String )
127         {
128             return ( ((String)obj).length() > 0
129                      ? Boolean.TRUE
130                      : Boolean.FALSE );
131         }
132         else 
133         {
134             // assume it's a node so that this node-set is non-empty 
135             // and so it's true
136             return ( obj != null ) ? Boolean.TRUE : Boolean.FALSE;
137         }
138 
139     }
140 }