01: // ============================================================================
02: // $Id: Constant.java,v 1.13 2006/01/08 00:52:25 davidahall Exp $
03: // Copyright (c) 2003-2005 David A. Hall
04: // ============================================================================
05: // The contents of this file are subject to the Common Development and
06: // Distribution License (CDDL), Version 1.0 (the License); you may not use this
07: // file except in compliance with the License. You should have received a copy
08: // of the the License along with this file: if not, a copy of the License is
09: // available from Sun Microsystems, Inc.
10: //
11: // http://www.sun.com/cddl/cddl.html
12: //
13: // From time to time, the license steward (initially Sun Microsystems, Inc.) may
14: // publish revised and/or new versions of the License. You may not use,
15: // distribute, or otherwise make this file available under subsequent versions
16: // of the License.
17: //
18: // Alternatively, the contents of this file may be used under the terms of the
19: // GNU Lesser General Public License Version 2.1 or later (the "LGPL"), in which
20: // case the provisions of the LGPL are applicable instead of those above. If you
21: // wish to allow use of your version of this file only under the terms of the
22: // LGPL, and not to allow others to use your version of this file under the
23: // terms of the CDDL, indicate your decision by deleting the provisions above
24: // and replace them with the notice and other provisions required by the LGPL.
25: // If you do not delete the provisions above, a recipient may use your version
26: // of this file under the terms of either the CDDL or the LGPL.
27: //
28: // This library is distributed in the hope that it will be useful,
29: // but WITHOUT ANY WARRANTY; without even the implied warranty of
30: // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
31: // ============================================================================
32:
33: package net.sf.jga.fn.adaptor;
34:
35: import net.sf.jga.fn.Generator;
36:
37: /**
38: * Functor that returns the constant value given at construction.
39: * <p>
40: * Copyright © 2003-2005 David A. Hall
41: *
42: * @author <a href="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
43: */
44:
45: public class Constant<V> extends Generator<V> {
46:
47: static final long serialVersionUID = 8451989044496281343L;
48:
49: private V _value;
50:
51: /**
52: * Builds a Constant functor for the given value. The value may be null:
53: * in that case, evaluating the functor will return null.
54: */
55: public Constant(V val) {
56: _value = val;
57: }
58:
59: // Generator interface
60:
61: /**
62: * Returns the constant value given at construction
63: * @return the constant value given at construction
64: */
65:
66: public V gen() {
67: return _value;
68: }
69:
70: /**
71: * Calls the Visitor's <code>visit(Constant)</code> method, if it
72: * implements the nested Visitor interface.
73: */
74: public void accept(net.sf.jga.fn.Visitor v) {
75: if (v instanceof Constant.Visitor)
76: ((Constant.Visitor) v).visit(this );
77: else
78: v.visit(this );
79: }
80:
81: // Object overrides
82:
83: public String toString() {
84: return "const " + _value;
85: }
86:
87: // AcyclicVisitor
88:
89: /**
90: * Interface for classes that may interpret a <b>Constant</b> generator.
91: */
92: public interface Visitor extends net.sf.jga.fn.Visitor {
93: public void visit(Constant host);
94: }
95: }
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