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 }