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


1 // ============================================================================
2 // $Id: Negate.java,v 1.13 2006/04/26 03:15:55 davidahall Exp $
3 // Copyright (c) 2003-2005 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.arithmetic;
34
35 import java.text.MessageFormat JavaDoc;
36 import net.sf.jga.fn.EvaluationException;
37 import net.sf.jga.fn.UnaryFunctor;
38
39 /**
40  * Returns the negative of its numeric argument.
41  * <p>
42  * Copyright &copy; 2003-2005 David A. Hall
43  *
44  * @author <a HREF="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
45  */
46
47 public class Negate<T extends Number JavaDoc> extends UnaryFunctor<T,T> {
48     
49     static final long serialVersionUID = -7631446216663885944L;
50
51     // Utility class that performs the addition as appropriate for the
52 // class given at construction
53 transient private Arithmetic<T> _math;
54
55     // The type of operands this instance supports
56 private Class JavaDoc<T> _type;
57      
58     /**
59      * Builds Negate functor for the given class. The class argument must
60      * be the same as the generic class argument (when generics are in use)
61      * or else a ClassCastException will be thrown when the functor is used.
62      *
63      * @throws IllegalArgumentException if the given class has no Arithmetic
64      * implementation registered with the ArithmeticFactory
65      */
66     public Negate(Class JavaDoc<T> c) {
67         _type = c;
68         getMath();
69     }
70     
71     /**
72      * Returns the type of operands this instance supports
73      */
74     public Class JavaDoc<T> getType() {
75         return _type;
76     }
77     
78     // Unary Functor interface
79
80     /**
81      * Given numeric argument <b>x</b>, returns -x
82      * @return the negative of its numeric argument
83      */
84     public T fn(T x) {
85          return getMath().negate(x);
86     }
87     
88     /**
89      * Calls the Visitor's <code>visit(Negate)</code> method, if it implements
90      * the nested Visitor interface.
91      */
92     public void accept(net.sf.jga.fn.Visitor v) {
93         if (v instanceof Negate.Visitor)
94             ((Negate.Visitor)v).visit(this);
95         else
96             v.visit(this);
97     }
98     
99     /**
100      */
101     private Arithmetic<T> getMath() {
102         if (_math == null) {
103             _math = ArithmeticFactory.getArithmetic(_type);
104             if (_math == null) {
105                 String JavaDoc msg = "No implementation of Arithmetic registered for {0}";
106                 throw new IllegalArgumentException JavaDoc(MessageFormat.format(msg, new Object JavaDoc[]{_type}));
107             }
108         }
109
110         return _math;
111     }
112     
113     // Object overrides
114
115     public String JavaDoc toString() {
116         return "Negate";
117     }
118     
119     // AcyclicVisitor
120
121     /**
122      * Interface for classes that may interpret a <b>Negate</b> functor.
123      */
124     public interface Visitor extends net.sf.jga.fn.Visitor {
125         public void visit(Negate host);
126     }
127 }
128
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