1 /*
2 * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/SumFunction.java,v 1.10 2005/06/28 13:44:45 elharo Exp $
3 * $Revision: 1.10 $
4 * $Date: 2005/06/28 13:44:45 $
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 1.10 2005/06/28 13:44:45 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 }