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1   /*
2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/PositionFunction.java,v 1.8 2005/06/26 16:07:23 elharo Exp $
3    * $Revision: 1.8 $
4    * $Date: 2005/06/26 16:07:23 $
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: PositionFunction.java,v 1.8 2005/06/26 16:07:23 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  
71  /***
72   * <p><b>4.1</b> <code><i>number</i> position()</code></p>
73   *
74   * 
75   * <blockquote src="http://www.w3.org/TR/xpath">
76   * The position function returns a number equal to the context position from the expression evaluation context.
77   * </blockquote>
78   * 
79   * @author bob mcwhirter (bob @ werken.com)
80   * @see <a href="http://www.w3.org/TR/xpath#function-position" target="_top">Section 4.1 of the XPath Specification</a>
81   */
82  public class PositionFunction implements Function
83  {
84      
85      /***
86       * Create a new <code>PositionFunction</code> object.
87       */
88      public PositionFunction() {}
89      
90      /***
91       * Returns the position of the context node in the context node-set.
92       * 
93       * @param context the context at the point in the
94       *         expression where the function is called
95       * @param args an empty list
96       * 
97       * @return a <code>Double</code> containing the context position
98       * 
99       * @throws FunctionCallException if <code>args</code> is not empty
100      * 
101      * @see Context#getSize()
102      */
103     public Object call(Context context, List args) throws FunctionCallException 
104     {
105         if ( args.size() == 0 )
106         {
107             return evaluate( context );
108         }
109         
110         throw new FunctionCallException( "position() requires no arguments." );
111     }
112     
113     /***
114      * 
115      * Returns the position of the context node in the context node-set.
116      * 
117      * @param context the context at the point in the
118      *         expression where the function is called
119      * 
120      * @return a <code>Double</code> containing the context position
121      * 
122      * @see Context#getPosition()
123      */
124     public static Double evaluate(Context context)
125     {
126         return new Double( context.getPosition() );
127     }
128     
129 }