001: // ============================================================================
002: // $Id: ConditionalBinary.java,v 1.7 2006/01/08 00:52:25 davidahall Exp $
003: // Copyright (c) 2002-2005 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.adaptor;
034:
035: import net.sf.jga.fn.BinaryFunctor;
036:
037: /**
038: * BinaryFunctor that tests a condition, executes one of two given functors, and
039: * returns the result. The arguments used to evaluate the condition will also
040: * be passed to whichever functor is executed. This functor implements the
041: * traditional <code><b>?:</b></code> operator.
042: * <p>
043: * Copyright © 2003-2005 David A. Hall
044: *
045: * @author <a href="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
046: **/
047:
048: public class ConditionalBinary<T1, T2, R> extends
049: BinaryFunctor<T1, T2, R> {
050:
051: static final long serialVersionUID = -2682605534388798188L;
052:
053: // The condition to be evaluated
054: private BinaryFunctor<T1, T2, Boolean> _test;
055:
056: // The functor to execute when the condition passes
057: private BinaryFunctor<T1, T2, R> _then;
058:
059: // The functor to execute when the condition fails
060: private BinaryFunctor<T1, T2, R> _else;
061:
062: /**
063: * Builds a ConditionalBinary functor, given the condition to test, and the two
064: * functors that may be executed.
065: * @throws IllegalArgumentException if any of the functors is missing
066: */
067: public ConditionalBinary(BinaryFunctor<T1, T2, Boolean> test,
068: BinaryFunctor<T1, T2, R> trueFn,
069: BinaryFunctor<T1, T2, R> falseFn) {
070: if (test == null || trueFn == null || falseFn == null) {
071: throw new IllegalArgumentException(
072: "Three functors are required");
073: }
074:
075: _test = test;
076: _then = trueFn;
077: _else = falseFn;
078: }
079:
080: /**
081: * Returns the test functors
082: * @return the test functors
083: */
084: public BinaryFunctor<T1, T2, Boolean> getCondition() {
085: return _test;
086: }
087:
088: /**
089: * Returns the functor that is executed when the condition is true
090: * @return the functor that is executed when the condition is true
091: */
092: public BinaryFunctor<T1, T2, R> getTrueFunctor() {
093: return _then;
094: }
095:
096: /**
097: * Returns the functor that is executed when the condition is false
098: * @return the functor that is executed when the condition is false
099: */
100: public BinaryFunctor<T1, T2, R> getFalseFunctor() {
101: return _else;
102: }
103:
104: // BinaryFunctor interface
105:
106: /**
107: * Given arguments <b>x</b> and <b>x</b> evaluates test(x,y); if true,
108: * returns trueFn(x,y), otherwise, returns falseFn(x,y).
109: *
110: * @return test(x,y) ? trueFn(x,y) : falseFn(x,y)
111: */
112: public R fn(T1 x, T2 y) {
113: return _test.fn(x, y) ? _then.fn(x, y) : _else.fn(x, y);
114: }
115:
116: /**
117: * Calls the Visitor's <code>visit(ConditionalBinary)</code> method, if it
118: * implements the nested Visitor interface.
119: */
120: public void accept(net.sf.jga.fn.Visitor v) {
121: if (v instanceof ConditionalBinary.Visitor)
122: ((ConditionalBinary.Visitor) v).visit(this );
123: else
124: v.visit(this );
125: }
126:
127: // Object overrides
128:
129: public String toString() {
130: return "ConditionalBinary[" + _test + "?" + _then + ":" + _else
131: + "]";
132: }
133:
134: // Acyclic Visitor
135:
136: /**
137: * Interface for classes that may interpret a <b>ConditionalBinary</b> functor.
138: */
139: public interface Visitor extends net.sf.jga.fn.Visitor {
140: public void visit(ConditionalBinary host);
141: }
142: }
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