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


1 // ============================================================================
2 // $Id: ChainBinary.java,v 1.9 2006/01/08 00:52:25 davidahall Exp $
3 // Copyright (c) 2002-2005 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.adaptor;
34
35 import net.sf.jga.fn.BinaryFunctor;
36 import net.sf.jga.fn.UnaryFunctor;
37
38 /**
39  * Binary Functor that passes the results of a Binary Functor as the argument
40  * to a Unary Functor. This allows for the construction of compound
41  * functors from the primitives found in the arithmetic, logical, property, and
42  * comparison packages.
43  * <p>
44  * Copyright &copy; 2002-2005 David A. Hall
45  *
46  * @author <a HREF="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
47  **/
48
49 public class ChainBinary<T1,T2,F,R> extends BinaryFunctor<T1,T2,R> {
50     
51     static final long serialVersionUID = -8161448545088932320L;
52
53     private UnaryFunctor<F,R> _f;
54     
55     private BinaryFunctor<T1,T2,F> _g;
56
57     /**
58      * Builds a ChainBinary functor, given outer functor <b>f</b> and inner
59      * functor <b>g</b>.
60      * @throws IllegalArgumentException if any of the functors is missing
61      */
62     public ChainBinary(UnaryFunctor<F,R> f, BinaryFunctor<T1,T2,F> g) {
63         if (f == null || g == null ) {
64             String JavaDoc msg = "Two functors are required";
65             throw new IllegalArgumentException JavaDoc(msg);
66         }
67         
68         _f = f; _g =g;;
69     }
70
71     /**
72      * Returns the outer functor
73      * @return the outer functor
74      */
75     public UnaryFunctor<F,R> getOuterFunctor() { return _f; }
76
77    /**
78      * Returns the inner functor
79      * @return the inner functor
80      */
81     public BinaryFunctor<T1,T2,F> getInnerFunctor() { return _g; }
82
83     // BinaryFunctor interface
84
85     /**
86      * Passes arguments <b>x</b> and <b>y</b> to the inner functor, and passes
87      * the result to the outer functor.
88      *
89      * @return f(g(x,y))
90      */
91     public R fn(T1 x, T2 y) {
92         return _f.fn(_g.fn(x,y));
93     }
94     
95     /**
96      * Calls the Visitor's <code>visit(ChainBinary)</code> method, if it
97      * implements the nested Visitor interface.
98      */
99     public void accept(net.sf.jga.fn.Visitor v) {
100         if (v instanceof ChainBinary.Visitor)
101             ((ChainBinary.Visitor)v).visit(this);
102         else
103             v.visit(this);
104     }
105
106     // Object overrides
107
108     public String JavaDoc toString() {
109         return _f+".compose("+_g+")";
110     }
111     
112     // Acyclic Visitor
113
114     /**
115      * Interface for classes that may interpret a <b>ChainBinary</b> functor.
116      */
117     public interface Visitor extends net.sf.jga.fn.Visitor {
118         public void visit(ChainBinary host);
119     }
120 }
121
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