/*
* $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 $
* $Revision: 1.11 $
* $Date: 2006/02/05 21:47:41 $
*
* ====================================================================
*
* Copyright 2000-2002 bob mcwhirter & James Strachan.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* * Neither the name of the Jaxen Project nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
* OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* ====================================================================
* This software consists of voluntary contributions made by many
* individuals on behalf of the Jaxen Project and was originally
* created by bob mcwhirter <bob@werken.com> and
* James Strachan <jstrachan@apache.org>. For more information on the
* Jaxen Project, please see <http://www.jaxen.org/>.
*
* $Id: SumFunction.java,v 1.11 2006/02/05 21:47:41 elharo Exp $
*/
package org.jaxen.function;
import java.util.Iterator;
import java.util.List;
import org.jaxen.Context;
import org.jaxen.Function;
import org.jaxen.FunctionCallException;
import org.jaxen.Navigator;
/**
* <p><b>4.4</b> <code><i>number</i> sum(<i>node-set</i>)</code> </p>
*
* <blockquote src="http://www.w3.org/TR/xpath#function-sum">
* The sum function returns the sum, for each node in the argument node-set,
* of the result of converting the string-values of the node to a number.
* </blockquote>
*
* @author bob mcwhirter (bob @ werken.com)
* @see <a href="http://www.w3.org/TR/xpath#function-sum" target="_top">Section 4.4 of the XPath Specification</a>
*/
public class SumFunction implements Function
{
/**
* Create a new <code>SumFunction</code> object.
*/
public SumFunction() {}
/** Returns the sum of its arguments.
*
* @param context the context at the point in the
* expression when the function is called
* @param args a list that contains exactly one item, also a <code>List</code>
*
* @return a <code>Double</code> containing the sum of the items in <code>args.get(0)</code>
*
* @throws FunctionCallException if <code>args</code> has more or less than one item;
* or if the first argument is not a <code>List</code>
*/
public Object call(Context context,
List args) throws FunctionCallException
{
if (args.size() == 1)
{
return evaluate( args.get(0),
context.getNavigator() );
}
throw new FunctionCallException( "sum() requires one argument." );
}
/**
* Returns the sum of the items in a list.
* If necessary, each item in the list is first converted to a <code>Double</code>
* as if by the XPath <code>number()</code> function.
*
* @param obj a <code>List</code> of numbers to be summed
* @param nav ignored
*
* @return the sum of the list
*
* @throws FunctionCallException if <code>obj</code> is not a <code>List</code>
*/
public static Double evaluate(Object obj,
Navigator nav) throws FunctionCallException
{
double sum = 0;
if (obj instanceof List)
{
Iterator nodeIter = ((List)obj).iterator();
while ( nodeIter.hasNext() )
{
double term = NumberFunction.evaluate( nodeIter.next(),
nav ).doubleValue();
sum += term;
}
}
else
{
throw new FunctionCallException("The argument to the sum function must be a node-set");
}
return new Double(sum);
}
}