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    1   /*
    2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/Function.java,v 1.7 2005/06/28 13:44:44 elharo Exp $
    3    * $Revision: 1.7 $
    4    * $Date: 2005/06/28 13:44:44 $
    5    *
    6    * ====================================================================
    7    *
    8    * Copyright (C) 2000-2002 bob mcwhirter & James Strachan.
    9    * All rights reserved.
    10   *
    11   * Redistribution and use in source and binary forms, with or without
    12   * modification, are permitted provided that the following conditions
    13   * are met:
    14   *
    15   * 1. Redistributions of source code must retain the above copyright
    16   *    notice, this list of conditions, and the following disclaimer.
    17   *
    18   * 2. Redistributions in binary form must reproduce the above copyright
    19   *    notice, this list of conditions, and the disclaimer that follows
    20   *    these conditions in the documentation and/or other materials
    21   *    provided with the distribution.
    22   *
    23   * 3. The name "Jaxen" must not be used to endorse or promote products
    24   *    derived from this software without prior written permission.  For
    25   *    written permission, please contact license@jaxen.org.
    26   *
    27   * 4. Products derived from this software may not be called "Jaxen", nor
    28   *    may "Jaxen" appear in their name, without prior written permission
    29   *    from the Jaxen Project Management (pm@jaxen.org).
    30   *
    31   * In addition, we request (but do not require) that you include in the
    32   * end-user documentation provided with the redistribution and/or in the
    33   * software itself an acknowledgement equivalent to the following:
    34   *     "This product includes software developed by the
    35   *      Jaxen Project <http://www.jaxen.org/>."
    36   * Alternatively, the acknowledgment may be graphical using the logos
    37   * available at http://www.jaxen.org/
    38   *
    39   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
    40   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    41   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    42   * DISCLAIMED.  IN NO EVENT SHALL THE Jaxen AUTHORS OR THE PROJECT
    43   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    44   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    45   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
    46   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
    47   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
    48   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
    49   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    50   * SUCH DAMAGE.
    51   *
    52   * ====================================================================
    53   * This software consists of voluntary contributions made by many
    54   * individuals on behalf of the Jaxen Project and was originally
    55   * created by bob mcwhirter <bob@werken.com> and
    56   * James Strachan <jstrachan@apache.org>.  For more information on the
    57   * Jaxen Project, please see <http://www.jaxen.org/>.
    58   *
    59   * $Id: Function.java,v 1.7 2005/06/28 13:44:44 elharo Exp $
    60   */
    61
    62
    63  package org.jaxen;
    64
    65  import java.util.List;
    66
    67  /*** Interface for the extensible function framework.
    68   *
    69   *  <p>
    70   *  <strong>NOTE:</strong> This class is not typically used directly,
    71   *  but is exposed for writers of extended XPath packages.
    72   *  </p>
    73   *
    74   *  <p>
    75   *  Implementations of <code>Function</code> are functors
    76   *  which are used to evaluate a function-call within an
    77   *  XPath expression.
    78   *  </p>
    79   *
    80   *  @see FunctionContext
    81   *
    82   *  @author <a href="mailto:bob@werken.com">bob mcwhirter</a>
    83   */
    84  public interface Function
    85  {
    86      /*** Evaluate this function.
    87       *
    88       * @param context the context at the point in the
    89       *         expression when the function is called
    90       * @param args arguments provided to the function
    91       *
    92       * @return the result of evaluating the function; a <code>List</code>
    93       *    (node-set), <code>Double</code>, <code>Boolean</code>, or
    94       *    <code>String</code>
    95       *
    96       * @throws FunctionCallException if an XPath error occurs during evaluation;
    97       *     for instance, if the number or type of the arguments is incorrect
    98       */
    99      Object call(Context context,
    100                 List args) throws FunctionCallException;
    101 }