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


1 // ============================================================================
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// $Id: ComposeBinary.java,v 1.9 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  * Binary Functor that passes the results of two inner Binary Functors as the
39  * arguments to an outer Binary Functor. This allows for the construction of
40  * compound functors from the primitives found in the arithmetic, logical,
41  * property, and comparison packages.
42  * <p>
43  * Copyright &copy; 2002-2005 David A. Hall
44  *
45  * @author <a HREF="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
46  **/

47
48 public class ComposeBinary<T1,T2,F1,F2,R> extends BinaryFunctor<T1,T2,R> {
49
50     static final long serialVersionUID = -6427141311027965863L;
51
52     // The first of two inner functors
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private BinaryFunctor<T1,T2,F1> _f;
54
55     // The second of two inner functors
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private BinaryFunctor<T1,T2,F2> _g;
57
58     // The outer functor
59
private BinaryFunctor<F1,F2,R> _h;
60
61     /**
62      * Builds a ComposeBinary functor, given two inner functors <b>f</b> and
63      * <b>g</b>, and outer functor <b>h</b>.
64      * @throws IllegalArgumentException if any of the functors is missing
65      */

66     public ComposeBinary(BinaryFunctor<T1,T2,F1> f,
67                          BinaryFunctor<T1,T2,F2> g,
68                          BinaryFunctor<F1,F2,R> h)
69     {
70         if (f == null || g == null || h == null) {
71             throw new IllegalArgumentException JavaDoc("Three functors are required");
72         }
73         
74         _f = f; _g =g; _h = h;
75     }
76
77     /**
78      * Returns the first of two inner functors
79      * @return the first of two inner functors
80      */

81     public BinaryFunctor<T1,T2,F1> getFirstInnerFunctor() { return _f; }
82
83     /**
84      * Returns the second of two inner functors
85      * @return the second of two inner functors
86      */

87     public BinaryFunctor<T1,T2,F2> getSecondInnerFunctor() { return _g; }
88
89     /**
90      * Returns the outer functor
91      * @return the outer functor
92      */

93     public BinaryFunctor<F1,F2,R> getOuterFunctor() { return _h; }
94
95     // BinaryFunctor interface
96

97     /**
98      * Given argument <b>x</b>, passes x to both inner functors, and passes the
99      * results of those functors to the outer functor.
100      *
101      * @return h(f(x,y), g(x,y))
102      */

103     public R fn(T1 x, T2 y) {
104         return _h.fn(_f.fn(x,y), _g.fn(x,y));
105     }
106     
107     /**
108      * Calls the Visitor's <code>visit(ComposeBinary)</code> method, if it
109      * implements the nested Visitor interface.
110      */

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

120     public String JavaDoc toString() {
121         return _h+".compose("+_f+","+_g+")";
122     }
123     
124     // Acyclic Visitor
125

126     /**
127      * Interface for classes that may interpret a <b>ComposeBinary</b> functor.
128      */

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