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/interpreter/tags/at2dist170907/src/edu/vub/at/objects/natives/grammar/AGTabulation.java

http://ambienttalk.googlecode.com/
Java | 94 lines | 39 code | 10 blank | 45 comment | 0 complexity | f05984757f82d5429a535b9916d2a435 MD5 | raw file
 1/**
 2 * AmbientTalk/2 Project
 3 * AGTabulation.java created on 26-jul-2006 at 16:19:54
 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.XIllegalIndex;
32import edu.vub.at.exceptions.XTypeMismatch;
33import edu.vub.at.objects.ATContext;
34import edu.vub.at.objects.ATNumber;
35import edu.vub.at.objects.ATObject;
36import edu.vub.at.objects.ATTable;
37import edu.vub.at.objects.grammar.ATExpression;
38import edu.vub.at.objects.grammar.ATTabulation;
39import edu.vub.at.objects.natives.NATText;
40
41/**
42 * @author tvc
43 *
44 * The native implementation of a tabulaton AG element.
45 */
46public final class AGTabulation extends AGExpression implements ATTabulation {
47
48	private final ATExpression tblExp_;
49	private final ATExpression idxExp_;
50	
51	public AGTabulation(ATExpression tbl, ATExpression idx) {
52		tblExp_ = tbl;
53		idxExp_ = idx;
54	}
55	
56	public ATExpression base_tableExpression() { return tblExp_; }
57
58	public ATExpression base_indexExpression() { return idxExp_; }
59
60	/**
61	 * To evaluate a tabulation, evaluate the tabulation expression to a table,
62	 * evaluate the index expression into a valid index, and then access the table at the given index slot.
63	 * 
64	 * AGTBL(tbl,idx).eval(ctx) = tbl.eval(ctx).at(idx.eval(ctx))
65	 * 
66	 * @return the value of the indexed table slot.
67	 */
68	public ATObject meta_eval(ATContext ctx) throws InterpreterException {
69		ATTable tab = tblExp_.meta_eval(ctx).asTable();
70		ATNumber idx = null;
71		try {
72			idx = idxExp_.meta_eval(ctx).asNumber();
73		} catch (XTypeMismatch e) {
74			throw new XIllegalIndex(e.getMessage());
75		}
76		return tab.base_at(idx);
77	}
78
79	/**
80	 * Quoting a tabulation results in a new quoted tabulation
81	 * 
82	 * AGTBL(tbl,idx).quote(ctx) = AGTBL(tbl.quote(ctx),idx.quote(ctx))
83	 */
84	public ATObject meta_quote(ATContext ctx) throws InterpreterException {
85		return new AGTabulation(tblExp_.meta_quote(ctx).asExpression(),
86				               idxExp_.meta_quote(ctx).asExpression());
87	}
88	
89	public NATText meta_print() throws InterpreterException {
90		return NATText.atValue(tblExp_.meta_print().javaValue + "[" +
91				              idxExp_.meta_print().javaValue + "]");
92	}
93	
94}