/interpreter/tags/at2-build270707/src/edu/vub/at/objects/natives/grammar/AGDefField.java

 1/**
 2 * AmbientTalk/2 Project
 3 * AGDefField.java created on 26-jul-2006 at 12:14:43
 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.ATDefField;
34import edu.vub.at.objects.grammar.ATExpression;
35import edu.vub.at.objects.grammar.ATSymbol;
36import edu.vub.at.objects.natives.NATText;
37
38/**
39 * @author tvc
40 *
41 * AGDefField represents the abstract grammar for defining fields.
42 * Examples:
43 *   <tt>x := 5</tt>
44 *   <tt>+ := "foo"</tt>
45 */
46public final class AGDefField extends NATAbstractGrammar implements ATDefField {
47
48	private final ATSymbol name_;
49	private final ATExpression valueExp_;
50	
51	public AGDefField(ATSymbol name, ATExpression value) {
52		name_ = name;
53		valueExp_ = value;
54	}
55	
56	public ATSymbol base_name() { return name_; }
57	public ATExpression base_valueExpression() { return valueExp_; }
58	
59	/**
60	 * Defines a new field in the current scope. The return value is
61	 * the evaluated value.
62	 * 
63	 * AGDEFFIELD(nam,val).eval(ctx) =
64	 *   ctx.scope.addField(nam, val.eval(ctx))
65	 */
66	public ATObject meta_eval(ATContext ctx) throws InterpreterException {
67		ATObject val = valueExp_.meta_eval(ctx);
68		ctx.base_lexicalScope().meta_defineField(name_, val);
69		return val;
70	}
71
72	/**
73	 * Quoting a field definition results in a new quoted field definition.
74	 * 
75	 * AGDEFFIELD(nam,val).quote(ctx) = AGDEFFIELD(nam.quote(ctx), val.quote(ctx))
76	 */
77	public ATObject meta_quote(ATContext ctx) throws InterpreterException {
78		return new AGDefField(name_.meta_quote(ctx).asSymbol(), valueExp_.meta_quote(ctx).asExpression());
79	}
80	
81	public NATText meta_print() throws InterpreterException {
82		return NATText.atValue("def " + name_.meta_print().javaValue + " := " + valueExp_.meta_print().javaValue);
83	}
84
85}