01: // ============================================================================
02: // $Id: Functor.java,v 1.2 2006/12/16 16:48:58 davidahall Exp $
03: // Copyright (c) 2006 David A. Hall
04: // ============================================================================
05: // The contents of this file are subject to the Common Development and
06: // Distribution License (CDDL), Version 1.0 (the License); you may not use this
07: // file except in compliance with the License. You should have received a copy
08: // of the the License along with this file: if not, a copy of the License is
09: // 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;
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 © 2006 David A. Hall
51: */
52:
53: abstract public class Functor<R> implements java.io.Serializable,
54: Visitable {
55:
56: /**
57: * A non-typesafe evaluation method for function objects. The number and
58: * types of arguments is not checked at compile time: an invalid number of
59: * arguments may cause IndexOutOfBoundsException (or cause extraneous
60: * arguments to be ignored); an argument of an invalid type may cause a
61: * ClassCastException.
62: */
63: abstract public R eval(Object... args);
64:
65: /**
66: * No-op implementation of Visitable interface.
67: */
68: public void accept(Visitor v) {
69: }
70: }
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