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


1 // ============================================================================
2 // $Id: Bind.java,v 1.8 2006/01/08 00:52:25 davidahall Exp $
3 // Copyright (c) 2004-2005 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.Generator;
36 import net.sf.jga.fn.UnaryFunctor;
37
38 /**
39  * Generator that wraps a given UnaryFunctor, passing a constant value
40  * as the argument of the child functor.
41  * <p>
42  * Copyright &copy; 2004-2005 David A. Hall
43  *
44  * @author <a HREF="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
45  **/
46
47 public class Bind<T, R> extends Generator<R> {
48
49     static final long serialVersionUID = -7970887561245835912L;
50     
51     // The functor whose argument is bound
52 private UnaryFunctor<T, R> _f;
53
54     // The value bound to the arg
55 private T _c;
56
57     /**
58      * Builds a Bind Functor with the given constant and child functor.
59      * @throws IllegalArgumentException if the functor is null.
60      */
61     public Bind(T constant, UnaryFunctor<T, R> fn) {
62         if (fn == null) {
63             throw new IllegalArgumentException JavaDoc("Must supply a function");
64         }
65             
66         _f = fn;
67         _c = constant;
68     }
69
70     /**
71      * Returns the child functor for this functor
72      * @return the child functor for this functor
73      */
74     public UnaryFunctor<T, R> getFunctor() { return _f; }
75
76     /**
77      * Returns the constant value
78      * @return the constant value
79      */
80     public T getConstant() { return _c; }
81
82     // UnaryFunctor interface
83
84     /**
85      * Given one argument, passes the constant value and the argument to the
86      * child functor and returns the result.
87      *
88      * @return f(c,x)
89      */
90     public R gen() {
91         return _f.fn(_c);
92     }
93
94     /**
95      * Calls the Visitor's <code>visit(Bind)</code> method, if it
96      * implements the nested Visitor interface.
97      */
98     public void accept(net.sf.jga.fn.Visitor v) {
99         if (v instanceof Bind.Visitor)
100             ((Bind.Visitor)v).visit(this);
101         else
102             v.visit(this);
103     }
104     
105     // Object overrides
106
107     public String JavaDoc toString() {
108         return _f+".bind("+_c+")";
109     }
110     
111     // AcyclicVisitor
112
113     /**
114      * Interface for classes that may interpret an <b>Bind</b> functor.
115      */
116     public interface Visitor extends net.sf.jga.fn.Visitor {
117         public void visit(Bind bf);
118     }
119 }
120
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