001: // ============================================================================
002: // $Id: Multiplies.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 product 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 Multiplies<T extends Number> extends
048: BinaryFunctor<T, T, T> {
049:
050: static final long serialVersionUID = -8859601644905516511L;
051:
052: // Utility class that performs the multiplication as appropriate for the
053: // class given at construction
054: transient private Arithmetic<T> _math;
055:
056: // The type of operands this instance supports
057: private Class<T> _type;
058:
059: /**
060: * Builds Multiplies functor for the given class. The class argument must
061: * be the same as the generic class argument (when generics are in use)
062: * or else a ClassCastException will be thrown when the functor is used.
063: *
064: * @throws IllegalArgumentException if the given class has no Arithmetic
065: * implementation registered with the ArithmeticFactory
066: */
067: public Multiplies(Class<T> c) {
068: _type = c;
069: getMath();
070: }
071:
072: /**
073: * Returns the type of operands this instance supports
074: */
075: public Class<T> getType() {
076: return _type;
077: }
078:
079: // Binary Functor interface
080:
081: /**
082: * Given numeric arguments <b>x</b> and <b>y</b>, returns x * y
083: * @return the product of two numeric arguments
084: */
085: public T fn(T x, T y) {
086: try {
087: return getMath().multiplies(x, y);
088: } catch (ClassCastException ex) {
089: String msg = "ClassCastException: Cannot multiply {0}[{1}] and {2}[{3}]";
090: String err = MessageFormat.format(msg, new Object[] {
091: x.getClass(), x, y.getClass(), y });
092: throw new EvaluationException(err, ex);
093: }
094: }
095:
096: /**
097: * Calls the Visitor's <code>visit(Multiplies)</code> method, if it
098: * implements the nested Visitor interface.
099: */
100: public void accept(net.sf.jga.fn.Visitor v) {
101: if (v instanceof Multiplies.Visitor)
102: ((Multiplies.Visitor) v).visit(this );
103: else
104: v.visit(this );
105: }
106:
107: /**
108: */
109: private Arithmetic<T> getMath() {
110: if (_math == null) {
111: _math = ArithmeticFactory.getArithmetic(_type);
112: if (_math == null) {
113: String msg = "No implementation of Arithmetic registered for {0}";
114: throw new IllegalArgumentException(MessageFormat
115: .format(msg, new Object[] { _type }));
116: }
117: }
118:
119: return _math;
120: }
121:
122: // Object overrides
123:
124: public String toString() {
125: return "Multiplies";
126: }
127:
128: // AcyclicVisitor
129:
130: /**
131: * Interface for classes that may interpret a <b>Multiplies</b> functor.
132: */
133: public interface Visitor extends net.sf.jga.fn.Visitor {
134: public void visit(Multiplies host);
135: }
136: }
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