1 /*
2 * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/SumFunction.java,v 1.11 2006/02/05 21:47:41 elharo Exp $
3 * $Revision: 1.11 $
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: SumFunction.java,v 1.11 2006/02/05 21:47:41 elharo Exp $
46 */
47
48
49 package org.jaxen.function;
50
51 import java.util.Iterator;
52 import java.util.List;
53
54 import org.jaxen.Context;
55 import org.jaxen.Function;
56 import org.jaxen.FunctionCallException;
57 import org.jaxen.Navigator;
58
59 /***
60 * <p><b>4.4</b> <code><i>number</i> sum(<i>node-set</i>)</code> </p>
61 *
62 * <blockquote src="http://www.w3.org/TR/xpath#function-sum">
63 * The sum function returns the sum, for each node in the argument node-set,
64 * of the result of converting the string-values of the node to a number.
65 * </blockquote>
66 *
67 * @author bob mcwhirter (bob @ werken.com)
68 * @see <a href="http://www.w3.org/TR/xpath#function-sum" target="_top">Section 4.4 of the XPath Specification</a>
69 */
70 public class SumFunction implements Function
71 {
72
73 /***
74 * Create a new <code>SumFunction</code> object.
75 */
76 public SumFunction() {}
77
78 /*** Returns the sum of its arguments.
79 *
80 * @param context the context at the point in the
81 * expression when the function is called
82 * @param args a list that contains exactly one item, also a <code>List</code>
83 *
84 * @return a <code>Double</code> containing the sum of the items in <code>args.get(0)</code>
85 *
86 * @throws FunctionCallException if <code>args</code> has more or less than one item;
87 * or if the first argument is not a <code>List</code>
88 */
89 public Object call(Context context,
90 List args) throws FunctionCallException
91 {
92
93 if (args.size() == 1)
94 {
95 return evaluate( args.get(0),
96 context.getNavigator() );
97 }
98
99 throw new FunctionCallException( "sum() requires one argument." );
100 }
101
102 /***
103 * Returns the sum of the items in a list.
104 * If necessary, each item in the list is first converted to a <code>Double</code>
105 * as if by the XPath <code>number()</code> function.
106 *
107 * @param obj a <code>List</code> of numbers to be summed
108 * @param nav ignored
109 *
110 * @return the sum of the list
111 *
112 * @throws FunctionCallException if <code>obj</code> is not a <code>List</code>
113 */
114 public static Double evaluate(Object obj,
115 Navigator nav) throws FunctionCallException
116 {
117 double sum = 0;
118
119 if (obj instanceof List)
120 {
121 Iterator nodeIter = ((List)obj).iterator();
122 while ( nodeIter.hasNext() )
123 {
124 double term = NumberFunction.evaluate( nodeIter.next(),
125 nav ).doubleValue();
126 sum += term;
127 }
128 }
129 else
130 {
131 throw new FunctionCallException("The argument to the sum function must be a node-set");
132 }
133
134 return new Double(sum);
135 }
136
137 }