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Java > Open Source Codes > net > sf > jga > fn > adaptor > ConditionalBinary


1 // ============================================================================
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// $Id: ConditionalBinary.java,v 1.7 2006/01/08 00:52:25 davidahall Exp $
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// Copyright (c) 2002-2005 David A. Hall
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// ============================================================================
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// The contents of this file are subject to the Common Development and
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// Distribution License (CDDL), Version 1.0 (the License); you may not use this
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// file except in compliance with the License. You should have received a copy
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// of the the License along with this file: if not, a copy of the License is
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// available from Sun Microsystems, Inc.
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//
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// http://www.sun.com/cddl/cddl.html
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//
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// From time to time, the license steward (initially Sun Microsystems, Inc.) may
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// publish revised and/or new versions of the License. You may not use,
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// distribute, or otherwise make this file available under subsequent versions
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// of the License.
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//
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// Alternatively, the contents of this file may be used under the terms of the
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// GNU Lesser General Public License Version 2.1 or later (the "LGPL"), in which
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// case the provisions of the LGPL are applicable instead of those above. If you
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// wish to allow use of your version of this file only under the terms of the
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// LGPL, and not to allow others to use your version of this file under the
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// terms of the CDDL, indicate your decision by deleting the provisions above
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// and replace them with the notice and other provisions required by the LGPL.
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// If you do not delete the provisions above, a recipient may use your version
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// of this file under the terms of either the CDDL or the LGPL.
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//
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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// ============================================================================
32

33 package net.sf.jga.fn.adaptor;
34
35 import net.sf.jga.fn.BinaryFunctor;
36
37 /**
38  * BinaryFunctor that tests a condition, executes one of two given functors, and
39  * returns the result. The arguments used to evaluate the condition will also
40  * be passed to whichever functor is executed. This functor implements the
41  * traditional <code><b>?:</b></code> operator.
42  * <p>
43  * Copyright &copy; 2003-2005 David A. Hall
44  *
45  * @author <a HREF="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
46  **/

47
48 public class ConditionalBinary<T1,T2,R> extends BinaryFunctor<T1,T2,R> {
49
50     static final long serialVersionUID = -2682605534388798188L;
51     
52     // The condition to be evaluated
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private BinaryFunctor<T1,T2,Boolean JavaDoc> _test;
54
55     // The functor to execute when the condition passes
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private BinaryFunctor<T1,T2,R> _then;
57
58     // The functor to execute when the condition fails
59
private BinaryFunctor<T1,T2,R> _else;
60
61     /**
62      * Builds a ConditionalBinary functor, given the condition to test, and the two
63      * functors that may be executed.
64      * @throws IllegalArgumentException if any of the functors is missing
65      */

66     public ConditionalBinary(BinaryFunctor<T1,T2,Boolean JavaDoc> test, BinaryFunctor<T1,T2,R> trueFn,
67                        BinaryFunctor<T1,T2,R> falseFn)
68     {
69         if (test == null || trueFn == null || falseFn == null) {
70             throw new IllegalArgumentException JavaDoc("Three functors are required");
71         }
72
73         _test = test;
74         _then = trueFn;
75         _else = falseFn;
76     }
77
78     /**
79      * Returns the test functors
80      * @return the test functors
81      */

82     public BinaryFunctor<T1,T2,Boolean JavaDoc> getCondition() { return _test; }
83
84     /**
85      * Returns the functor that is executed when the condition is true
86      * @return the functor that is executed when the condition is true
87      */

88     public BinaryFunctor<T1,T2,R> getTrueFunctor() { return _then; }
89
90     /**
91      * Returns the functor that is executed when the condition is false
92      * @return the functor that is executed when the condition is false
93      */

94     public BinaryFunctor<T1,T2,R> getFalseFunctor() { return _else; }
95
96     // BinaryFunctor interface
97

98     /**
99      * Given arguments <b>x</b> and <b>x</b> evaluates test(x,y); if true,
100      * returns trueFn(x,y), otherwise, returns falseFn(x,y).
101      *
102      * @return test(x,y) ? trueFn(x,y) : falseFn(x,y)
103      */

104     public R fn(T1 x, T2 y) {
105         return _test.fn(x,y) ? _then.fn(x,y) : _else.fn(x,y);
106     }
107     
108     /**
109      * Calls the Visitor's <code>visit(ConditionalBinary)</code> method, if it
110      * implements the nested Visitor interface.
111      */

112     public void accept(net.sf.jga.fn.Visitor v) {
113         if (v instanceof ConditionalBinary.Visitor)
114             ((ConditionalBinary.Visitor)v).visit(this);
115         else
116             v.visit(this);
117     }
118
119     // Object overrides
120

121     public String JavaDoc toString() {
122         return "ConditionalBinary["+_test+"?"+_then+":"+_else+"]";
123     }
124     
125     // Acyclic Visitor
126

127     /**
128      * Interface for classes that may interpret a <b>ConditionalBinary</b> functor.
129      */

130     public interface Visitor extends net.sf.jga.fn.Visitor {
131         public void visit(ConditionalBinary host);
132     }
133 }
134
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