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1 /*
2  * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/Function.java,v 1.6 2005/04/29 02:25:56 elharo Exp $
3  * $Revision: 1.6 $
4  * $Date: 2005/04/29 02:25:56 $
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 1.6 2005/04/29 02:25:56 elharo Exp $
60  */
61
62
63 package org.jaxen;
64
65 import java.util.List JavaDoc;
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 JavaDoc call(Context context,
100                 List JavaDoc args) throws FunctionCallException;
101 }
102
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