SumFunction


1   /*
2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/SumFunction.java,v 1.9 2005/06/26 16:07:23 elharo Exp $
3    * $Revision: 1.9 $
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: SumFunction.java,v 1.9 2005/06/26 16:07:23 elharo Exp $
60   */
61  
62  
63  package org.jaxen.function;
64  
65  import java.util.Iterator  ;
66  import java.util.List  ;
67  
68  import org.jaxen.Context;
69  import org.jaxen.Function;
70  import org.jaxen.FunctionCallException;
71  import org.jaxen.Navigator;
72  
73  /**
74   * <p><b>4.4</b> <code><i>number</i> sum(<i>node-set</i>)</code> </p>
75   * 
76   * <blockquote SRC="http://www.w3.org/TR/xpath#function-sum">
77   * The sum function returns the sum, for each node in the argument node-set, 
78   * of the result of converting the string-values of the node to a number.
79   * </blockquote>
80   * 
81   * @author bob mcwhirter (bob @ werken.com)
82   * @see <a HREF="http://www.w3.org/TR/xpath#function-sum" target="_top">Section 4.4 of the XPath Specification</a>
83   */
84  public class SumFunction implements Function
85  {
86  
87      /**
88       * Create a new <code>SumFunction</code> object.
89       */
90      public SumFunction() {}
91      
92      /** Returns the sum of its arguments.
93       *
94       * @param context the context at the point in the
95       *         expression when the function is called
96       * @param args a list that contains exactly one item, also a <code>List</code>
97       * 
98       * @return a <code>Double</code> containing the sum of the items in <code>args.get(0)</code>
99       * 
100      * @throws FunctionCallException if <code>args</code> has more or less than one item;
101      *     or if the first argument is not a <code>List</code>
102      */
103     public Object   call(Context context,
104                        List   args) throws FunctionCallException
105     {
106 
107         if (args.size() == 1)
108         {
109             return evaluate( args.get(0),
110                              context.getNavigator() );
111         }
112 
113         throw new FunctionCallException( "sum() requires one argument." );
114     }
115 
116     /** 
117      * Returns the sum of the items in a list.
118      * If necessary, each item in the list is first converted to a <code>Double</code>
119      * as if by the XPath <code>number()</code> function.
120      * 
121      * @param obj a <code>List</code> of numbers to be summed
122      * @param nav ignored
123      * 
124      * @return the sum of the list
125      * 
126      * @throws FunctionCallException if <code>obj</code> is not a <code>List</code>
127      */
128     public static Double   evaluate(Object   obj,
129                                   Navigator nav) throws FunctionCallException
130     {
131         double sum  = 0;
132 
133         if (obj instanceof List  )
134         {
135             Iterator   nodeIter = ((List  )obj).iterator();
136             while ( nodeIter.hasNext() )
137             {
138                 double term = NumberFunction.evaluate( nodeIter.next(),
139                                                 nav ).doubleValue();
140                 sum += term;
141             }
142         }
143         else
144         {
145             throw new FunctionCallException("The argument to the sum function must be a node-set");
146         }
147 
148         return new Double  (sum);
149     }
150     
151 }
152
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