/*

 * Copyright (c) 2003, 2005, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

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>

 * @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;

}