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Java > Open Source Codes > net > sf > jga > fn > Functor


1 // ============================================================================
2 // $Id: Functor.java,v 1.2 2006/12/16 16:48:58 davidahall Exp $
3 // Copyright (c) 2006 David A. Hall
4 // ============================================================================
5 // The contents of this file are subject to the Common Development and
6 // Distribution License (CDDL), Version 1.0 (the License); you may not use this
7 // file except in compliance with the License. You should have received a copy
8 // of the the License along with this file: if not, a copy of the License is
9 // available from Sun Microsystems, Inc.
10 //
11 // http://www.sun.com/cddl/cddl.html
12 //
13 // From time to time, the license steward (initially Sun Microsystems, Inc.) may
14 // publish revised and/or new versions of the License. You may not use,
15 // distribute, or otherwise make this file available under subsequent versions
16 // of the License.
17 //
18 // Alternatively, the contents of this file may be used under the terms of the
19 // GNU Lesser General Public License Version 2.1 or later (the "LGPL"), in which
20 // case the provisions of the LGPL are applicable instead of those above. If you
21 // wish to allow use of your version of this file only under the terms of the
22 // LGPL, and not to allow others to use your version of this file under the
23 // terms of the CDDL, indicate your decision by deleting the provisions above
24 // and replace them with the notice and other provisions required by the LGPL.
25 // If you do not delete the provisions above, a recipient may use your version
26 // of this file under the terms of either the CDDL or the LGPL.
27 //
28 // This library is distributed in the hope that it will be useful,
29 // but WITHOUT ANY WARRANTY; without even the implied warranty of
30 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
31 // ============================================================================
32
33 package net.sf.jga.fn;
34
35 import java.io.Serializable JavaDoc;
36
37 /**
38  * A Function object that accepts an arbitrary number of arguments and returns
39  * a value of type R. The Functor interface is generally not typesafe. It is
40  * typesafe with respect to the return type (R), but the compiler cannot ensure
41  * that the number of arguments or their types are appropriate for any given
42  * implementation of the Functor interface. However, three direct subclasses,
43  * Generator<R>, UnaryFunctor<T,R>, and BindaryFunctor<T1,T2,R> are typesafe,
44  * provided their interfaces are used in leiu of this interface.
45  * <p>
46  * In short, if you want the compiler to enforce type safetype with respect to
47  * the number and type of arguments, then do not use the method(s) defined by
48  * this class: use the methods defined by the typesafe derived classes.
49  * <p>
50  * Copyright &copy; 2006 David A. Hall
51  */
52
53 abstract public class Functor<R> implements java.io.Serializable JavaDoc, Visitable {
54
55     /**
56      * A non-typesafe evaluation method for function objects. The number and
57      * types of arguments is not checked at compile time: an invalid number of
58      * arguments may cause IndexOutOfBoundsException (or cause extraneous
59      * arguments to be ignored); an argument of an invalid type may cause a
60      * ClassCastException.
61      */
62     abstract public R eval(Object JavaDoc... args);
63     
64     /**
65      * No-op implementation of Visitable interface.
66      */
67     public void accept(Visitor v) {}
68 }
69
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