/interpreter/tags/at2dist041108/src/edu/vub/at/objects/natives/grammar/AGLookup.java

 1/**
 2 * AmbientTalk/2 Project
 3 * AGApplication.java created on 10-jul-2007 at 10:13:31
 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;
33import edu.vub.at.objects.grammar.ATLookup;
34import edu.vub.at.objects.grammar.ATSymbol;
35import edu.vub.at.objects.natives.NATText;
36
37import java.util.HashSet;
38import java.util.Set;
39
40/**
41 * The native implementation of a lexical lookup AG element.
42 * Example: <tt>&foo</tt>
43 * 
44 * @author smostinc
45 */
46public final class AGLookup extends AGExpression implements ATLookup {
47
48	private final ATSymbol selector_;
49	
50	/** construct a new lookup AG element */
51	public AGLookup(ATSymbol fun) {
52		selector_ = fun;
53	}
54	
55	public ATSymbol base_selector() { return selector_; }
56
57	/**
58	 * To evaluate a lexical lookup, the function name is sought for in the lexical scope.
59	 * 
60	 * AGLKU(nam).eval(ctx) = ctx.lex.lookup(nam)
61	 * 
62	 * @return a closure containing the requested function.
63	 */
64	public ATObject meta_eval(ATContext ctx) throws InterpreterException {
65		return ctx.base_lexicalScope().impl_lookup(selector_);
66	}
67
68	/**
69	 * Quoting a lookup results in a new quoted lookup.
70	 * 
71	 * AGAPL(sel,arg).quote(ctx) = AGAPL(sel.quote(ctx), arg.quote(ctx))
72	 */
73	public ATObject meta_quote(ATContext ctx) throws InterpreterException {
74		return new AGLookup(selector_.meta_quote(ctx).asSymbol());
75	}
76	
77	public NATText meta_print() throws InterpreterException {
78		return NATText.atValue("&" + selector_.meta_print().javaValue);
79	}
80	
81	/**
82	 * FV(&nam) = { nam }
83	 */
84	public Set impl_freeVariables() throws InterpreterException {
85        HashSet singleton = new HashSet();
86        singleton.add(selector_);
87        return singleton;
88	}
89	
90	public Set impl_quotedFreeVariables() throws InterpreterException {
91		return selector_.impl_quotedFreeVariables();
92	}
93
94}