View Javadoc

1   /*
2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/RoundFunction.java,v 1.10 2005/06/26 16:07:22 elharo Exp $
3    * $Revision: 1.10 $
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: RoundFunction.java,v 1.10 2005/06/26 16:07:22 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>4.4</b> <code><i>number</i> round(<i>number</i>)</code> </p>
74   * 
75   * 
76   * <blockquote src="http://www.w3.org/TR/xpath">
77   * The <b>round</b> function returns the number that is closest to the argument and that is an integer. 
78   * If there are two such numbers, then the one that is closest to positive infinity is returned. 
79   * If the argument is NaN, then NaN is returned. If the argument is positive infinity, then positive infinity is returned. 
80   * If the argument is negative infinity, then negative infinity is returned. 
81   * If the argument is positive zero, then positive zero is returned. 
82   * If the argument is negative zero, then negative zero is returned. 
83   * If the argument is less than zero, but greater than or equal to -0.5, then negative zero is returned.
84   * </blockquote>
85   * 
86   * @author bob mcwhirter (bob @ werken.com)
87   * 
88   * @see <a href="http://www.w3.org/TR/xpath#function-round" target="_top">Section 4.4 of the XPath Specification</a>
89   */
90  public class RoundFunction implements Function
91  {
92   
93      /***
94       * Create a new <code>RoundFunction</code> object.
95       */
96      public RoundFunction() {}
97      
98      
99      /*** Returns the nearest integer to the number.
100      *
101      * @param context the context at the point in the
102      *         expression when the function is called
103      * @param args a list with exactly one item which will be converted to a 
104      *     <code>Double</code> as if by the XPath <code>number()</code> function
105      * 
106      * @return a <code>Double</code> containing the integer nearest to
107      *     <code>args.get(0)</code>
108      * 
109      * @throws FunctionCallException if <code>args</code> has more or less than one item
110      */
111     public Object call(Context context,
112                        List args) throws FunctionCallException
113     {
114         if (args.size() == 1)
115         {
116             return evaluate( args.get(0),
117                              context.getNavigator() );
118         }
119 
120         throw new FunctionCallException( "round() requires one argument." );
121     }
122 
123     /*** 
124      * Returns the integer nearest to the argument.
125      * If necessary, the argument is first converted to a <code>Double</code>
126      * as if by the XPath <code>number()</code> function.
127      * 
128      * @param obj the object to be rounded
129      * @param nav ignored
130      * 
131      * @return the integer nearest to <code>obj</code>
132      */
133     public static Double evaluate(Object obj,
134                                   Navigator nav)
135     {
136         Double d  = NumberFunction.evaluate( obj,
137                                             nav );
138 
139         if (d.isNaN() || d.isInfinite())
140         {
141             return d;
142         }
143 
144         double value = d.doubleValue();
145         return new Double( Math.round( value ) );
146     }
147 }