001: // ============================================================================
002: // $Id: ValueOf.java,v 1.6 2006/01/08 00:52:25 davidahall Exp $
003: // Copyright (c) 2004-2005 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.EvaluationException;
037: import net.sf.jga.fn.UnaryFunctor;
038:
039: /**
040: * Returns the value of its numeric argument, converted to the approprate
041: * class.
042: * <p>
043: * Copyright © 2004-2005 David A. Hall
044: *
045: * @author <a href="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
046: */
047:
048: public class ValueOf<T extends Number, R extends Number> extends
049: UnaryFunctor<T, R> {
050:
051: static final long serialVersionUID = -5844974650711636917L;
052:
053: private Arithmetic<R> _math;
054:
055: private Class<R> _class;
056:
057: /**
058: * Builds ValueOf functor for the given class. The class argument must
059: * be the same as the generic class argument (when generics are in use)
060: * or else a ClassCastException will be thrown when the functor is used.
061: *
062: * @throws IllegalArgumentException if the given class has no Arithmetic
063: * implementation registered with the ArithmeticFactory
064: */
065: public ValueOf(Class<R> c) {
066: _class = c;
067: _math = ArithmeticFactory.getArithmetic(c);
068: if (_math == null) {
069: String msg = "No implementation of Arithmetic registered for {0}";
070: throw new IllegalArgumentException(MessageFormat.format(
071: msg, new Object[] { c }));
072: }
073: }
074:
075: // Unary Functor interface
076:
077: /**
078: * Given numeric argument <b>x</b>, converts x to the type passed at construction
079: * @return the converted version of its numeric argument
080: */
081: public R fn(T x) {
082: return _math.valueOf(x);
083: }
084:
085: /**
086: * Calls the Visitor's <code>visit(ValueOf)</code> method, if it implements
087: * the nested Visitor interface.
088: */
089: public void accept(net.sf.jga.fn.Visitor v) {
090: if (v instanceof ValueOf.Visitor)
091: ((ValueOf.Visitor) v).visit(this );
092: else
093: v.visit(this );
094: }
095:
096: // Object overrides
097:
098: public String toString() {
099: return "ValueOf[" + _class.getName() + "]";
100: }
101:
102: // AcyclicVisitor
103:
104: /**
105: * Interface for classes that may interpret a <b>ValueOf</b> functor.
106: */
107: public interface Visitor extends net.sf.jga.fn.Visitor {
108: public void visit(ValueOf host);
109: }
110: }
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