/interpreter/tags/at2dist090708/src/edu/vub/at/objects/natives/grammar/AGSelf.java

 1/**
 2 * AmbientTalk/2 Project
 3 * AGSelf.java created on 27-jul-2006 at 12:57:41
 4 * (c) Programming Technology Lab, 2006 - 2007
 5 * Authors: Tom Van Cutsem & Stijn Mostinckx
 6 * 
 7 * Permission is hereby granted, free of charge, to any person
 8 * obtaining a copy of this software and associated documentation
 9 * files (the "Software"), to deal in the Software without
10 * restriction, including without limitation the rights to use,
11 * copy, modify, merge, publish, distribute, sublicense, and/or
12 * sell copies of the Software, and to permit persons to whom the
13 * Software is furnished to do so, subject to the following
14 * conditions:
15 *
16 * The above copyright notice and this permission notice shall be
17 * included in all copies or substantial portions of the Software.
18 *
19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
20 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
21 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
22 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
23 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
24 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
25 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
26 * OTHER DEALINGS IN THE SOFTWARE.
27 */
28package edu.vub.at.objects.natives.grammar;
29
30import edu.vub.at.exceptions.InterpreterException;
31import edu.vub.at.objects.ATContext;
32import edu.vub.at.objects.ATObject;
33
34/**
35 * @author tvc
36 *
37 * The abstract grammar element denoting the symbol 'self'
38 */
39public final class AGSelf extends AGSymbol {
40
41	private static final String SELF_NAM = "self";
42	
43	public static final AGSelf _INSTANCE_ = new AGSelf();
44	
45	private AGSelf() { super(SELF_NAM); }
46	
47	/**
48	 * To evaluate a self reference, simply select the current self from the current evaluation context.
49	 * 
50	 * AGSelf().eval(ctx) = ctx.self
51	 */
52	public ATObject meta_eval(ATContext ctx) throws InterpreterException {
53		return ctx.base_receiver();
54	}
55
56	/**
57	 * Quoting a self reference results in the same self reference.
58	 */
59	public ATObject meta_quote(ATContext ctx) {
60		return this;
61	}
62	
63	/**
64	 * After deserialization, ensure that the self pseudovariable remains unique.
65	 */
66	public ATObject meta_resolve() throws InterpreterException {
67		return _INSTANCE_;
68	}
69	
70}