001: // ============================================================================
002: // $Id: ComposeBinary.java,v 1.9 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: * Binary Functor that passes the results of two inner Binary Functors as the
039: * arguments to an outer Binary Functor. This allows for the construction of
040: * compound functors from the primitives found in the arithmetic, logical,
041: * property, and comparison packages.
042: * <p>
043: * Copyright © 2002-2005 David A. Hall
044: *
045: * @author <a href="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
046: **/
047:
048: public class ComposeBinary<T1, T2, F1, F2, R> extends
049: BinaryFunctor<T1, T2, R> {
050:
051: static final long serialVersionUID = -6427141311027965863L;
052:
053: // The first of two inner functors
054: private BinaryFunctor<T1, T2, F1> _f;
055:
056: // The second of two inner functors
057: private BinaryFunctor<T1, T2, F2> _g;
058:
059: // The outer functor
060: private BinaryFunctor<F1, F2, R> _h;
061:
062: /**
063: * Builds a ComposeBinary functor, given two inner functors <b>f</b> and
064: * <b>g</b>, and outer functor <b>h</b>.
065: * @throws IllegalArgumentException if any of the functors is missing
066: */
067: public ComposeBinary(BinaryFunctor<T1, T2, F1> f,
068: BinaryFunctor<T1, T2, F2> g, BinaryFunctor<F1, F2, R> h) {
069: if (f == null || g == null || h == null) {
070: throw new IllegalArgumentException(
071: "Three functors are required");
072: }
073:
074: _f = f;
075: _g = g;
076: _h = h;
077: }
078:
079: /**
080: * Returns the first of two inner functors
081: * @return the first of two inner functors
082: */
083: public BinaryFunctor<T1, T2, F1> getFirstInnerFunctor() {
084: return _f;
085: }
086:
087: /**
088: * Returns the second of two inner functors
089: * @return the second of two inner functors
090: */
091: public BinaryFunctor<T1, T2, F2> getSecondInnerFunctor() {
092: return _g;
093: }
094:
095: /**
096: * Returns the outer functor
097: * @return the outer functor
098: */
099: public BinaryFunctor<F1, F2, R> getOuterFunctor() {
100: return _h;
101: }
102:
103: // BinaryFunctor interface
104:
105: /**
106: * Given argument <b>x</b>, passes x to both inner functors, and passes the
107: * results of those functors to the outer functor.
108: *
109: * @return h(f(x,y), g(x,y))
110: */
111: public R fn(T1 x, T2 y) {
112: return _h.fn(_f.fn(x, y), _g.fn(x, y));
113: }
114:
115: /**
116: * Calls the Visitor's <code>visit(ComposeBinary)</code> method, if it
117: * implements the nested Visitor interface.
118: */
119: public void accept(net.sf.jga.fn.Visitor v) {
120: if (v instanceof ComposeBinary.Visitor)
121: ((ComposeBinary.Visitor) v).visit(this );
122: else
123: v.visit(this );
124: }
125:
126: // Object overrides
127:
128: public String toString() {
129: return _h + ".compose(" + _f + "," + _g + ")";
130: }
131:
132: // Acyclic Visitor
133:
134: /**
135: * Interface for classes that may interpret a <b>ComposeBinary</b> functor.
136: */
137: public interface Visitor extends net.sf.jga.fn.Visitor {
138: public void visit(ComposeBinary host);
139: }
140: }
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