/interpreter/tags/at2dist130208/src/edu/vub/at/objects/natives/grammar/AGUnquoteSplice.java

 1/**
 2 * AmbientTalk/2 Project
 3 * AGUnquoteSplice.java created on 26-jul-2006 at 16:31:07
 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.exceptions.XIllegalQuote;
32import edu.vub.at.exceptions.XIllegalUnquote;
33import edu.vub.at.objects.ATContext;
34import edu.vub.at.objects.ATObject;
35import edu.vub.at.objects.grammar.ATExpression;
36import edu.vub.at.objects.grammar.ATUnquoteSplice;
37import edu.vub.at.objects.natives.NATText;
38
39/**
40 * @author tvc
41 *
42 * The native implementation of an unquote-splice AG element.
43 */
44public class AGUnquoteSplice extends AGExpression implements ATUnquoteSplice {
45
46	private final ATExpression uqsExp_;
47	
48	public AGUnquoteSplice(ATExpression exp) {
49		uqsExp_ = exp;
50	}
51	
52	public ATExpression base_expression() { return uqsExp_; }
53
54	/**
55	 * An unquotation cannot be evaluated, but rather gives rise to an XIllegalUnquote exception.
56	 * This is because an unquotation should always be nested within a quotation.
57	 * 
58	 * AGUQS(exp).eval(ctx) = ERROR
59	 */
60	public ATObject meta_eval(ATContext ctx) throws InterpreterException {
61		throw new XIllegalUnquote(uqsExp_);
62	}
63
64	/**
65	 * Quoting a spliced unquotation means evaluating its contained expression, and returning
66	 * its value as the result of the quote. A spliced unquotation can normally only
67	 * be invoked where a table or begin is expected. The resulting table is replaced by the result of
68	 * evaluating the unquote-splice's encapsulated expression.
69	 * 
70	 * It is the table's responsibility to query an AGUnquoteSplice element for its expression and deal with the inlining appropriately.
71	 */
72	public ATObject meta_quote(ATContext ctx) throws InterpreterException {
73		throw new XIllegalQuote(uqsExp_.meta_print().javaValue);
74	}
75	
76	public NATText meta_print() throws InterpreterException {
77		return NATText.atValue("#@("+ uqsExp_.meta_print().javaValue + ")");
78	}
79	
80	public boolean isUnquoteSplice() {
81		return true;
82	}
83	
84	public ATUnquoteSplice asUnquoteSplice() {
85		return this;
86	}
87
88}