1 /* 2 * $Header$ 3 * $Revision$ 4 * $Date$ 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 * $Id$ 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 cite="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="https://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 }