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


1 // ============================================================================
2 // $Id: ChainUnary.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.UnaryFunctor;
36 import net.sf.jga.fn.UnaryFunctor;
37
38 /**
39  * Unary Functor that passes the results of one Unary Functor as the argument
40  * to another 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 ChainUnary<T,F,R> extends UnaryFunctor<T,R> {
50
51     static final long serialVersionUID = -6690274081307420708L;
52
53     // the outer fn
54 private UnaryFunctor<F,R> _f;
55
56     // the inner fn
57 private UnaryFunctor<T,F> _g;
58     
59     /**
60      * Builds a BinaryCompose functor, given the outer functor <b>f</b> the
61      * inner functor <b>g</b>.
62      * @throws IllegalArgumentException if any of the functors is missing
63      */
64     public ChainUnary(UnaryFunctor<F,R> f, UnaryFunctor<T,F> g)
65     {
66         if (f == null || g == null) {
67             throw new IllegalArgumentException JavaDoc("Two functors are required");
68         }
69         
70         _f = f;
71         _g = g;
72     }
73
74     /**
75      * Returns the outer functor
76      * @return the outer functor
77      */
78     public UnaryFunctor<F,R> getOuterFunctor() { return _f; }
79     
80     /**
81      * Returns the inner functor
82      * @return the inner functor
83      */
84     public UnaryFunctor<T,F> getInnerFunctor() { return _g; }
85
86     // UnaryFunctor interface
87
88     /**
89      * Given argument <b>x</b>, passes x to the inner functor, and passes the
90      * result to the outer functor.
91      *
92      * @return f(g(x))
93      */
94     public R fn(T x) {
95         return _f.fn(_g.fn(x));
96     }
97
98     // Object overrides
99
100     public String JavaDoc toString() {
101         return _f+".compose("+_g+")";
102     }
103     
104     /**
105      * Calls the Visitor's <code>visit(BinaryCompose)</code> method, if it
106      * implements the nested Visitor interface.
107      */
108     public void accept(net.sf.jga.fn.Visitor v) {
109         if (v instanceof ChainUnary.Visitor)
110             ((ChainUnary.Visitor)v).visit(this);
111         else
112             v.visit(this);
113     }
114     
115     // AcyclicVisitor
116
117     /**
118      * Interface for classes that may interpret a <b>ChainUnary</b> functor.
119      */
120     public interface Visitor extends net.sf.jga.fn.Visitor {
121         public void visit(ChainUnary bf);
122     }
123 }
124
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