/*
 * The contents of this file are subject to the terms
 * of the Common Development and Distribution License
 * (the "License").  You may not use this file except
 * in compliance with the License.
 *
 * You can obtain a copy of the license at
 * https://jaxp.dev.java.net/CDDLv1.0.html.
 * See the License for the specific language governing
 * permissions and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL
 * HEADER in each file and include the License file at
 * https://jaxp.dev.java.net/CDDLv1.0.html
 * If applicable add the following below this CDDL HEADER
 * with the fields enclosed by brackets "[]" replaced with
 * your own identifying information: Portions Copyright
 * [year] [name of copyright owner]
 */

/*
 * $Id: XMLEntityReader.java,v 1.3 2005/11/03 17:02:21 jeffsuttor Exp $
 * @(#)XPathFunction.java	1.13 05/11/17
 *
 * Copyright 2006 Sun Microsystems, Inc. All Rights Reserved.
 */

package javax.xml.xpath;

import java.util.List;

/**
 * <p><code>XPathFunction</code> provides access to XPath functions.</p>
 *
 * <p>Functions are identified by QName and arity in XPath.</p>
 *
 * @author  <a href="mailto:Norman.Walsh@Sun.com">Norman Walsh</a>
 * @author  <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a>
 * @version $Revision: 1.2 $, $Date: 2005/06/10 03:50:44 $
 * @since 1.5
 */
public interface XPathFunction {
  /**
   * <p>Evaluate the function with the specified arguments.</p>
   *
   * <p>To the greatest extent possible, side-effects should be avoided in the
   * definition of extension functions. The implementation evaluating an
   * XPath expression is under no obligation to call extension functions in
   * any particular order or any particular number of times.</p>
   * 
   * @param args The arguments, <code>null</code> is a valid value.
   * 
   * @return The result of evaluating the <code>XPath</code> function as an <code>Object</code>.
   * 
   * @throws XPathFunctionException If <code>args</code> cannot be evaluated with this <code>XPath</code> function.
   */
  public Object evaluate(List args)
    throws XPathFunctionException;
}