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

 1/**
 2 * AmbientTalk/2 Project
 3 * AGQuote.java created on 26-jul-2006 at 16:26:41
 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;
33import edu.vub.at.objects.grammar.ATQuote;
34import edu.vub.at.objects.grammar.ATStatement;
35import edu.vub.at.objects.natives.NATText;
36
37import java.util.HashSet;
38import java.util.Set;
39
40/**
41 * @author tvc
42 *
43 * The native implementation of a quotation AG element.
44 */
45public final class AGQuote extends AGExpression implements ATQuote {
46
47	private final ATStatement stmt_;
48	
49	public AGQuote(ATStatement stmt) {
50		stmt_ = stmt;
51	}
52	
53	public ATStatement base_statement() { return stmt_; }
54
55	/**
56	 * To evaluate a quotation, start quoting its contained statement.
57	 * This recursive quoting is necessary in order to properly unquote nested unquotations.
58	 * 
59	 * AGQUO(stmt).eval(ctx) = stmt.quote(ctx)
60	 * 
61	 * @return the quoted statement
62	 */
63	public ATObject meta_eval(ATContext ctx) throws InterpreterException {
64		return stmt_.meta_quote(ctx);
65	}
66
67	/**
68	 * Quoting a quotation results in a bare quotation, where quotations and unquotations are left unexpanded.
69	 */
70	public ATObject meta_quote(ATContext ctx) throws InterpreterException {
71		return this;
72	}
73	
74	public NATText meta_print() throws InterpreterException {
75		return NATText.atValue("`("+ stmt_.meta_print().javaValue + ")");
76	}
77	
78	public ATQuote asQuote() throws InterpreterException {
79		return this;
80	}
81	
82	/**
83	 * FV(`exp) = FV_in_unquoted_expressions(exp)
84	 */
85	public Set impl_freeVariables() throws InterpreterException {
86		return stmt_.impl_quotedFreeVariables();
87	}
88	
89	/**
90	 * The expression `( `(x + #(y)) ) has no free variables.
91	 * It is assumed that the inner quotation is returned bare (without expansion)
92	 */
93	public Set impl_quotedFreeVariables() throws InterpreterException {
94		return new HashSet();
95	}
96
97}