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1   /*
2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/NotFunction.java,v 1.7 2005/06/26 16:07:22 elharo Exp $
3    * $Revision: 1.7 $
4    * $Date: 2005/06/26 16:07:22 $
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: NotFunction.java,v 1.7 2005/06/26 16:07:22 elharo Exp $
60   */
61  
62  package org.jaxen.function;
63  
64  import java.util.List;
65  
66  import org.jaxen.Context;
67  import org.jaxen.Function;
68  import org.jaxen.FunctionCallException;
69  import org.jaxen.Navigator;
70  
71  /***
72   * <p><b>4.3</b> <code><i>boolean</i> not(<i>boolean</i>)</code> </p>
73   * 
74   * 
75   * <blockquote src="http://www.w3.org/TR/xpath#function-not">
76   * The <b>not</b> function returns true if its argument is false, and false otherwise.
77   * </blockquote>
78   * 
79   * @author bob mcwhirter (bob @ werken.com)
80   * @see <a href="http://www.w3.org/TR/xpath#function-not" target="_top">Section 4.3 of the XPath Specification</a>
81   */
82  public class NotFunction implements Function
83  {
84  
85      /***
86       * Create a new <code>NotFunction</code> object.
87       */
88      public NotFunction() {}
89      
90      /***
91       * Returns <code>Boolean.TRUE</code> if the boolean value of 
92       * <code>args.get(0)</code> is false, and <code>Boolean.FALSE</code> otherwise.
93       * The boolean value is calculated as if by the XPath <code>boolean</code>
94       * function. 
95       * 
96       * @param context the context at the point in the
97       *         expression where the function is called
98       * @param args a single element list
99       * 
100      * @return <code>Boolean.TRUE</code> if the boolean value of 
101      * <code>obj</code> is false, and <code>Boolean.FALSE</code> otherwise
102      * 
103      * @throws FunctionCallException if <code>args</code> does not have exactly one argument
104      */
105     public Object call(Context context,
106                        List args) throws FunctionCallException
107     {
108         if (args.size() == 1)
109         {
110             return evaluate( args.get(0), context.getNavigator() );
111         }
112 
113         throw new FunctionCallException( "not() requires one argument." );
114     }
115 
116     /***
117      * Returns <code>Boolean.TRUE</code> if the boolean value of 
118      * <code>obj</code> is false, and <code>Boolean.FALSE</code> otherwise.
119      * The boolean value is calculated as if by the XPath <code>boolean</code>
120      * function. 
121      * 
122      * @param obj the object whose boolean value is inverted
123      * @param nav the <code>Navigator</code> used to calculate the boolean value of <code>obj</code>
124      * 
125      * @return <code>Boolean.TRUE</code> if the boolean value of 
126      * <code>obj</code> is false, and <code>Boolean.FALSE</code> otherwise
127      */
128     public static Boolean evaluate(Object obj, Navigator nav)
129     {
130         return ( ( BooleanFunction.evaluate( obj, nav ).booleanValue() )
131                  ? Boolean.FALSE
132                  : Boolean.TRUE
133                  );
134     }
135     
136 }