/*
* $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/NumberFunction.java,v 1.18 2006/02/05 21:47:41 elharo Exp $
* $Revision: 1.18 $
* $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: NumberFunction.java,v 1.18 2006/02/05 21:47:41 elharo Exp $
*/
package org.orbeon.jaxen.function;
import org.orbeon.jaxen.Context;
import org.orbeon.jaxen.Function;
import org.orbeon.jaxen.FunctionCallException;
import org.orbeon.jaxen.Navigator;
import java.util.Iterator;
import java.util.List;
/**
* <p>
* <b>4.4</b> <code><i>number</i> number(<i>object</i>)</code>
*
*
* <blockquote src="http://www.w3.org/TR/xpath#function-number">
* <p>
* The <b>number</b> function converts
* its argument to a number as follows:
* </p>
*
* <ul>
*
* <li>
* <p>
* a string that consists of optional whitespace followed by an optional
* minus sign followed by a <a href="#NT-Number">Number</a> followed by
* whitespace is converted to the IEEE 754 number that is nearest
* (according to the IEEE 754 round-to-nearest rule) to the mathematical
* value represented by the string; any other string is converted to NaN
* </p>
* </li>
*
* <li>
* <p>
* boolean true is converted to 1; boolean false is converted to 0
* </p>
* </li>
*
* <li>
*
* <p>
* a node-set is first converted to a string as if by a call to the <b><a
* href="http://www.w3.org/TR/xpath#function-string" target="_top">string</a></b> function and then converted
* in the same way as a string argument
* </p>
*
* </li>
*
* <li>
* <p>
* an object of a type other than the four basic types is converted to a
* number in a way that is dependent on that type
* </p>
* </li>
*
* </ul>
*
* <p>
* If the argument is omitted, it defaults to a node-set with the
* context node as its only member.
* </p>
*
* <blockquote> <b>NOTE: </b>The <b>number</b>
* function should not be used for conversion of numeric data occurring
* in an element in an XML document unless the element is of a type that
* represents numeric data in a language-neutral format (which would
* typically be transformed into a language-specific format for
* presentation to a user). In addition, the <b>number</b> function cannot be used
* unless the language-neutral format used by the element is consistent
* with the XPath syntax for a <a href="http://www.w3.org/TR/xpath#NT-Number">Number</a>.</blockquote>
*
* </blockquote>
*
* @author bob mcwhirter (bob @ werken.com)
*
* @see <a href="http://www.w3.org/TR/xpath#function-number"
* target="_top">Section 4.4 of the XPath Specification</a>
*/
public class NumberFunction implements Function
{
private final static Double NaN = new Double( Double.NaN );
/**
* Create a new <code>NumberFunction</code> object.
*/
public NumberFunction() {}
/**
* Returns the number value of <code>args.get(0)</code>,
* or the number value of the context node if <code>args</code>
* is empty.
*
* @param context the context at the point in the
* expression when the function is called
* @param args a list containing the single item to be converted to a
* <code>Double</code>
*
* @return a <code>Double</code>
*
* @throws FunctionCallException if <code>args</code> has more than one item
*/
public Object call(Context context, List args) throws FunctionCallException
{
if (args.size() == 1)
{
return evaluate( args.get(0), context.getNavigator() );
}
else if (args.size() == 0)
{
return evaluate( context.getNodeSet(), context.getNavigator() );
}
throw new FunctionCallException( "number() takes at most one argument." );
}
/**
* Returns the number value of <code>obj</code>.
*
* @param obj the object to be converted to a number
* @param nav the <code>Navigator</code> used to calculate the string-value
* of node-sets
*
* @return a <code>Double</code>
*/
public static Double evaluate(Object obj, Navigator nav)
{
if( obj instanceof Double )
{
return (Double) obj;
}
else if ( obj instanceof String )
{
String str = (String) obj;
try
{
Double doubleValue = new Double( str );
return doubleValue;
}
catch (NumberFormatException e)
{
return NaN;
}
}
else if ( obj instanceof List || obj instanceof Iterator )
{
return evaluate( StringFunction.evaluate( obj, nav ), nav );
}
else if ( nav.isElement( obj ) || nav.isAttribute( obj ) )
{
return evaluate( StringFunction.evaluate( obj, nav ), nav );
}
else if ( obj instanceof Boolean )
{
if ( obj == Boolean.TRUE )
{
return new Double( 1 );
}
else
{
return new Double( 0 );
}
}
return NaN;
}
/**
* Determines whether the argument is not a number (NaN) as defined
* by IEEE 754.
*
* @param val the double to test
* @return true if the value is NaN, false otherwise
*/
public static boolean isNaN( double val )
{
return Double.isNaN(val);
}
/**
* Determines whether the argument is not a number (NaN) as defined
* by IEEE 754.
*
* @param val the <code>Double</code> to test
* @return true if the value is NaN, false otherwise
*/
public static boolean isNaN( Double val )
{
return val.equals( NaN );
}
}