1. /*

  2.  * Copyright 1999-2004 The Apache Software Foundation

  3.  *

  4.  * Licensed under the Apache License, Version 2.0 (the "License");

  5.  * you may not use this file except in compliance with the License.

  6.  * You may obtain a copy of the License at

  7.  *

  8.  *     http://www.apache.org/licenses/LICENSE-2.0

  9.  *

  10.  * Unless required by applicable law or agreed to in writing, software

  11.  * distributed under the License is distributed on an "AS IS" BASIS,

  12.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  13.  * See the License for the specific language governing permissions and

  14.  * limitations under the License.

  15.  */

  16. package org.apache.commons.jxpath;

  17. 

  18. /**

  19.  * Extension function interface. Extension functions are grouped into

  20.  * {@link Functions Functions} objects, which are installed on

  21.  * JXPathContexts using the 

  22.  * {@link JXPathContext#setFunctions JXPathContext.setFunctions()}

  23.  * call.

  24.  * <p>

  25.  * The Function interface can be implemented directly. However,

  26.  * most of the time JXPath's built-in implementations should suffice.

  27.  * See {@link ClassFunctions ClassFunctions} and 

  28.  * {@link PackageFunctions PackageFunctions}.

  29.  *

  30.  * @author Dmitri Plotnikov

  31.  * @version $Revision: 1.7 $ $Date: 2004/02/29 14:17:42 $

  32.  */

  33. public interface Function {

  34. 

  35.     /**

  36.      * Computes the value of the function. Each implementation of Function

  37.      * is responsible for conversion of supplied parameters to the required

  38.      * argument types.

  39.      *

  40.      * @param context can be used to acquire the context in which the

  41.      *    function is being evaluted.

  42.      */

  43.     Object invoke(ExpressionContext context, Object[] parameters);

  44. }