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Java > Open Source Codes > net > sf > jga > fn > arithmetic > ShiftRight


1 // ============================================================================
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// $Id: ShiftRight.java,v 1.7 2006/04/26 03:15:56 davidahall Exp $
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// Copyright (c) 2003-2005 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.arithmetic;
34
35 import java.text.MessageFormat JavaDoc;
36 import net.sf.jga.fn.BinaryFunctor;
37 import net.sf.jga.fn.EvaluationException;
38
39 /**
40  * Returns the first argument shifted right by the number of places given in the
41  * second argument.
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 ShiftRight<T extends Number JavaDoc> extends BinaryFunctor<T,Integer JavaDoc,T> {
49     
50     static final long serialVersionUID = 4910289709792083209L;
51     
52     // Utility class that performs the bitwise shift as appropriate for the
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// class given at construction
54
transient private IntegerArithmetic<T> _math;
55      
56     // The type of operands this instance supports
57
private Class JavaDoc<T> _type;
58      
59     /**
60      * Builds ShiftRight functor for the given class. The class argument must
61      * be the same as the generic class argument (when generics are in use)
62      * or else a ClassCastException will be thrown when the functor is used.
63      *
64      * @throws IllegalArgumentException if the given class has no Arithmetic
65      * implementation registered with the ArithmeticFactory
66      */

67     public ShiftRight(Class JavaDoc<T> c) {
68         _type = c;
69         getMath();
70     }
71     
72     /**
73      * Returns the type of operands this instance supports
74      */

75     public Class JavaDoc<T> getType() {
76         return _type;
77     }
78     
79     // Binary Functor interface
80

81     /**
82      * Given integral arguments <b>x</b> and <b>y</b>, returns x &gt;&gt; y
83      * @return returns x &gt;&gt; y
84      */

85     public T fn(T x, Integer JavaDoc y) {
86         try {
87             return getMath().signedShiftRight(x, y);
88         }
89         catch (ClassCastException JavaDoc ex) {
90             String JavaDoc msg = "ClassCastException: Cannot compute shiftRight of {0}[{1}] and {2}[{3}]";
91             String JavaDoc err = MessageFormat.format(msg, new Object JavaDoc[]{ x.getClass(), x, y.getClass(), y});
92             throw new EvaluationException(err, ex);
93         }
94     }
95     
96     /**
97      * Calls the Visitor's <code>visit(ShiftRight)</code> method, if it implements
98      * the nested Visitor interface.
99      */

100     public void accept(net.sf.jga.fn.Visitor v) {
101         if (v instanceof ShiftRight.Visitor)
102             ((ShiftRight.Visitor)v).visit(this);
103         else
104             v.visit(this);
105     }
106     
107     /**
108      */

109     private IntegerArithmetic<T> getMath() {
110         if (_math == null) {
111             _math = ArithmeticFactory.getIntegralArithmetic(_type);
112             if (_math == null) {
113                 String JavaDoc msg = "No implementation of Arithmetic registered for {0}";
114                 throw new IllegalArgumentException JavaDoc(MessageFormat.format(msg, new Object JavaDoc[]{_type}));
115             }
116         }
117
118         return _math;
119     }
120     
121     // Object overrides
122

123     public String JavaDoc toString() {
124         return "ShiftRight";
125     }
126     
127     // AcyclicVisitor
128

129     /**
130      * Interface for classes that may interpret a <b>ShiftRight</b> functor.
131      */

132     public interface Visitor extends net.sf.jga.fn.Visitor {
133         public void visit(ShiftRight host);
134     }
135 }
136
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