001: // ============================================================================
002: // $Id: Bind.java,v 1.8 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.adaptor;
034:
035: import net.sf.jga.fn.Generator;
036: import net.sf.jga.fn.UnaryFunctor;
037:
038: /**
039: * Generator that wraps a given UnaryFunctor, passing a constant value
040: * as the argument of the child functor.
041: * <p>
042: * Copyright © 2004-2005 David A. Hall
043: *
044: * @author <a href="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
045: **/
046:
047: public class Bind<T, R> extends Generator<R> {
048:
049: static final long serialVersionUID = -7970887561245835912L;
050:
051: // The functor whose argument is bound
052: private UnaryFunctor<T, R> _f;
053:
054: // The value bound to the arg
055: private T _c;
056:
057: /**
058: * Builds a Bind Functor with the given constant and child functor.
059: * @throws IllegalArgumentException if the functor is null.
060: */
061: public Bind(T constant, UnaryFunctor<T, R> fn) {
062: if (fn == null) {
063: throw new IllegalArgumentException("Must supply a function");
064: }
065:
066: _f = fn;
067: _c = constant;
068: }
069:
070: /**
071: * Returns the child functor for this functor
072: * @return the child functor for this functor
073: */
074: public UnaryFunctor<T, R> getFunctor() {
075: return _f;
076: }
077:
078: /**
079: * Returns the constant value
080: * @return the constant value
081: */
082: public T getConstant() {
083: return _c;
084: }
085:
086: // UnaryFunctor interface
087:
088: /**
089: * Given one argument, passes the constant value and the argument to the
090: * child functor and returns the result.
091: *
092: * @return f(c,x)
093: */
094: public R gen() {
095: return _f.fn(_c);
096: }
097:
098: /**
099: * Calls the Visitor's <code>visit(Bind)</code> method, if it
100: * implements the nested Visitor interface.
101: */
102: public void accept(net.sf.jga.fn.Visitor v) {
103: if (v instanceof Bind.Visitor)
104: ((Bind.Visitor) v).visit(this );
105: else
106: v.visit(this );
107: }
108:
109: // Object overrides
110:
111: public String toString() {
112: return _f + ".bind(" + _c + ")";
113: }
114:
115: // AcyclicVisitor
116:
117: /**
118: * Interface for classes that may interpret an <b>Bind</b> functor.
119: */
120: public interface Visitor extends net.sf.jga.fn.Visitor {
121: public void visit(Bind bf);
122: }
123: }
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