001: // ============================================================================
002: // $Id: ConstantBinary.java,v 1.6 2006/01/08 00:52:25 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.adaptor;
034:
035: import net.sf.jga.fn.BinaryFunctor;
036:
037: /**
038: * Functor that returns the constant value given at construction.
039: * <p>
040: * To Serialize a ConstantBinary, the generic parameter V must be serializable.
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 ConstantBinary<T1, T2, V> extends BinaryFunctor<T1, T2, V> {
048:
049: static final long serialVersionUID = 2834438191454731796L;
050:
051: // The constant value.
052: private V _value;
053:
054: /**
055: * Builds a Constant functor for the given value. The value may be null:
056: * in that case, evaluating the functor will return null.
057: */
058: public ConstantBinary(V val) {
059: _value = val;
060: }
061:
062: // BinaryFunctor interface
063:
064: /**
065: * Given two arguments, ignores both and returns the constant value given
066: * at construction. Neither argument will be evaluated in any way by this
067: * functor.
068: *
069: * @return the constant value given at construction
070: */
071:
072: public V fn(T1 unused, T2 ignored) {
073: return _value;
074: }
075:
076: /**
077: * Calls the Visitor's <code>visit(Constant)</code> method, if it
078: * implements the nested Visitor interface.
079: */
080: public void accept(net.sf.jga.fn.Visitor v) {
081: if (v instanceof ConstantBinary.Visitor)
082: ((ConstantBinary.Visitor) v).visit(this );
083: else
084: v.visit(this );
085: }
086:
087: // Object overrides
088:
089: public String toString() {
090: return "const " + _value;
091: }
092:
093: // AcyclicVisitor
094:
095: /**
096: * Interface for classes that may interpret a <b>ConstantBinary</b> functor.
097: */
098: public interface Visitor extends net.sf.jga.fn.Visitor {
099: public void visit(ConstantBinary host);
100: }
101: }
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