001: // ============================================================================
002: // $Id: Minus.java,v 1.14 2006/04/26 03:15:55 davidahall Exp $
003: // Copyright (c) 2003-2005 David A. Hall
004: // ============================================================================
005: // The contents of this file are subject to the Common Development and
006: // Distribution License (CDDL), Version 1.0 (the License); you may not use this
007: // file except in compliance with the License. You should have received a copy
008: // of the the License along with this file: if not, a copy of the License is
009: // available from Sun Microsystems, Inc.
010: //
011: // http://www.sun.com/cddl/cddl.html
012: //
013: // From time to time, the license steward (initially Sun Microsystems, Inc.) may
014: // publish revised and/or new versions of the License. You may not use,
015: // distribute, or otherwise make this file available under subsequent versions
016: // of the License.
017: //
018: // Alternatively, the contents of this file may be used under the terms of the
019: // GNU Lesser General Public License Version 2.1 or later (the "LGPL"), in which
020: // case the provisions of the LGPL are applicable instead of those above. If you
021: // wish to allow use of your version of this file only under the terms of the
022: // LGPL, and not to allow others to use your version of this file under the
023: // terms of the CDDL, indicate your decision by deleting the provisions above
024: // and replace them with the notice and other provisions required by the LGPL.
025: // If you do not delete the provisions above, a recipient may use your version
026: // of this file under the terms of either the CDDL or the LGPL.
027: //
028: // This library is distributed in the hope that it will be useful,
029: // but WITHOUT ANY WARRANTY; without even the implied warranty of
030: // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
031: // ============================================================================
032:
033: package net.sf.jga.fn.arithmetic;
034:
035: import java.text.MessageFormat;
036: import net.sf.jga.fn.BinaryFunctor;
037: import net.sf.jga.fn.EvaluationException;
038:
039: /**
040: * Returns the difference of two numeric arguments.
041: * <p>
042: * Copyright © 2003-2005 David A. Hall
043: *
044: * @author <a href="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
045: */
046:
047: public class Minus<T extends Number> extends BinaryFunctor<T, T, T> {
048:
049: static final long serialVersionUID = -93265923560446089L;
050:
051: // Utility class that performs the subtraction as appropriate for the
052: // class given at construction
053: transient private Arithmetic<T> _math;
054:
055: // The type of operands this instance supports
056: private Class<T> _type;
057:
058: /**
059: * Builds Minus functor for the given class. The class argument must
060: * be the same as the generic class argument (when generics are in use)
061: * or else a ClassCastException will be thrown when the functor is used.
062: *
063: * @throws IllegalArgumentException if the given class has no Arithmetic
064: * implementation registered with the ArithmeticFactory
065: */
066: public Minus(Class<T> c) {
067: _type = c;
068: getMath();
069: }
070:
071: /**
072: * Returns the type of operands this instance supports
073: */
074: public Class<T> getType() {
075: return _type;
076: }
077:
078: // Binary Functor interface
079:
080: /**
081: * Given numeric arguments <b>x</b> and <b>y</b>, returns x - y
082: * @return the difference of two numeric arguments
083: */
084: public T fn(T x, T y) {
085: try {
086: return getMath().minus(x, y);
087: } catch (ClassCastException ex) {
088: String msg = "ClassCastException: Cannot subtract {2}[{3}] from {0}[{1}]";
089: String err = MessageFormat.format(msg, new Object[] {
090: x.getClass(), x, y.getClass(), y });
091: throw new EvaluationException(err, ex);
092: }
093: }
094:
095: /**
096: * Calls the Visitor's <code>visit(Minus)</code> method, if it implements
097: * the nested Visitor interface.
098: */
099: public void accept(net.sf.jga.fn.Visitor v) {
100: if (v instanceof Minus.Visitor)
101: ((Minus.Visitor) v).visit(this );
102: else
103: v.visit(this );
104: }
105:
106: /**
107: */
108: private Arithmetic<T> getMath() {
109: if (_math == null) {
110: _math = ArithmeticFactory.getArithmetic(_type);
111: if (_math == null) {
112: String msg = "No implementation of Arithmetic registered for {0}";
113: throw new IllegalArgumentException(MessageFormat
114: .format(msg, new Object[] { _type }));
115: }
116: }
117:
118: return _math;
119: }
120:
121: // Object overrides
122:
123: public String toString() {
124: return "Minus";
125: }
126:
127: // AcyclicVisitor
128:
129: /**
130: * Interface for classes that may interpret a <b>Minus</b> functor.
131: */
132: public interface Visitor extends net.sf.jga.fn.Visitor {
133: public void visit(Minus host);
134: }
135: }
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