/*
 * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/TrueFunction.java,v 1.9 2006/02/05 21:47:41 elharo Exp $
 * $Revision: 1.9 $
 * $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: TrueFunction.java,v 1.9 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 java.util.List;

/**
 * <p><b>4.3</b> <code><i>boolean</i> true()</code></p>
 *
 * <p>Returns true.</p>
 *
 * @author bob mcwhirter (bob @ werken.com)
 *
 * @see <a href="http://www.w3.org/TR/xpath#function-true">XPath Specification</a>
 */
public class TrueFunction implements Function
{

    /**
     * Create a new <code>TrueFunction</code> object.
     */
    public TrueFunction() {}


    /** Returns <code>Boolean.TRUE</code>
     *
     * @param context ignored
     * @param args an empty list
     *
     * @return <code>Boolean.TRUE</code>
     *
     * @throws FunctionCallException if <code>args</code> is not empty
     */
    public Object call(Context context,
                       List args) throws FunctionCallException
    {
        if (args.size() == 0)
        {
            return evaluate();
        }

        throw new FunctionCallException( "true() requires no arguments." );
    }

    /**
     * Returns true.
     *
     * @return <code>Boolean.TRUE</code>
     */
    public static Boolean evaluate()
    {
        return Boolean.TRUE;
    }
}