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1   /*
2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/RoundFunction.java,v 1.12 2006/02/05 21:47:41 elharo Exp $
3    * $Revision: 1.12 $
4    * $Date: 2006/02/05 21:47:41 $
5    *
6    * ====================================================================
7    *
8    * Copyright 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 are
13   * met:
14   * 
15   *   * Redistributions of source code must retain the above copyright
16   *     notice, this list of conditions and the following disclaimer.
17   * 
18   *   * Redistributions in binary form must reproduce the above copyright
19   *     notice, this list of conditions and the following disclaimer in the
20   *     documentation and/or other materials provided with the distribution.
21   * 
22   *   * Neither the name of the Jaxen Project nor the names of its
23   *     contributors may be used to endorse or promote products derived 
24   *     from this software without specific prior written permission.
25   * 
26   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
27   * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28   * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
29   * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
30   * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
31   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
32   * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
33   * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
34   * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
35   * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
36   * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37   *
38   * ====================================================================
39   * This software consists of voluntary contributions made by many 
40   * individuals on behalf of the Jaxen Project and was originally 
41   * created by bob mcwhirter <bob@werken.com> and 
42   * James Strachan <jstrachan@apache.org>.  For more information on the 
43   * Jaxen Project, please see <http://www.jaxen.org/>.
44   * 
45   * $Id: RoundFunction.java,v 1.12 2006/02/05 21:47:41 elharo Exp $
46   */
47  
48  
49  package org.jaxen.function;
50  
51  import java.util.List;
52  
53  import org.jaxen.Context;
54  import org.jaxen.Function;
55  import org.jaxen.FunctionCallException;
56  import org.jaxen.Navigator;
57  
58  /***
59   * <p><b>4.4</b> <code><i>number</i> round(<i>number</i>)</code> </p>
60   * 
61   * 
62   * <blockquote src="http://www.w3.org/TR/xpath">
63   * The <b>round</b> function returns the number that is closest to the argument and that is an integer. 
64   * If there are two such numbers, then the one that is closest to positive infinity is returned. 
65   * If the argument is NaN, then NaN is returned. If the argument is positive infinity, then positive infinity is returned. 
66   * If the argument is negative infinity, then negative infinity is returned. 
67   * If the argument is positive zero, then positive zero is returned. 
68   * If the argument is negative zero, then negative zero is returned. 
69   * If the argument is less than zero, but greater than or equal to -0.5, then negative zero is returned.
70   * </blockquote>
71   * 
72   * @author bob mcwhirter (bob @ werken.com)
73   * 
74   * @see <a href="http://www.w3.org/TR/xpath#function-round" target="_top">Section 4.4 of the XPath Specification</a>
75   */
76  public class RoundFunction implements Function
77  {
78   
79      /***
80       * Create a new <code>RoundFunction</code> object.
81       */
82      public RoundFunction() {}
83      
84      
85      /*** Returns the nearest integer to the number.
86       *
87       * @param context the context at the point in the
88       *         expression when the function is called
89       * @param args a list with exactly one item which will be converted to a 
90       *     <code>Double</code> as if by the XPath <code>number()</code> function
91       * 
92       * @return a <code>Double</code> containing the integer nearest to
93       *     <code>args.get(0)</code>
94       * 
95       * @throws FunctionCallException if <code>args</code> has more or less than one item
96       */
97      public Object call(Context context,
98                         List args) throws FunctionCallException
99      {
100         if (args.size() == 1)
101         {
102             return evaluate( args.get(0),
103                              context.getNavigator() );
104         }
105 
106         throw new FunctionCallException( "round() requires one argument." );
107     }
108 
109     /*** 
110      * Returns the integer nearest to the argument.
111      * If necessary, the argument is first converted to a <code>Double</code>
112      * as if by the XPath <code>number()</code> function.
113      * 
114      * @param obj the object to be rounded
115      * @param nav ignored
116      * 
117      * @return the integer nearest to <code>obj</code>
118      */
119     public static Double evaluate(Object obj,
120                                   Navigator nav)
121     {
122         Double d  = NumberFunction.evaluate( obj,
123                                             nav );
124 
125         if (d.isNaN() || d.isInfinite())
126         {
127             return d;
128         }
129 
130         double value = d.doubleValue();
131         return new Double( Math.round( value ) );
132     }
133 }