/interpreter/tags/at2-build060407/src/edu/vub/at/objects/natives/grammar/AGAssignVariable.java

 1/**
 2 * AmbientTalk/2 Project
 3 * AGAssignVariable.java created on 26-jul-2006 at 15:54:48
 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.XTypeMismatch;
32import edu.vub.at.objects.ATContext;
33import edu.vub.at.objects.ATObject;
34import edu.vub.at.objects.grammar.ATAssignVariable;
35import edu.vub.at.objects.grammar.ATExpression;
36import edu.vub.at.objects.grammar.ATSymbol;
37import edu.vub.at.objects.natives.NATText;
38
39/**
40 * @author tvc
41 *
42 * The native implementation of a variable assignment AG element.
43 * Examples:
44 *  <tt>x := 5</tt>
45 *  <tt>+ := m()</tt>
46 */
47public final class AGAssignVariable extends NATAbstractGrammar implements ATAssignVariable {
48
49	private final ATSymbol variableName_;
50	private final ATExpression valueExp_;
51	
52	public AGAssignVariable(ATSymbol nam, ATExpression val) {
53		variableName_ = nam;
54		valueExp_ = val;
55	}
56	
57	public ATSymbol base_getName() { return variableName_; }
58
59	public ATExpression base_getValueExpression() { return valueExp_; }
60
61	/**
62	 * To evaluate a variable assignment, evaluate the right hand side and ask
63	 * the current object to assign that value to the field corresponding to the left hand side.
64	 * 
65	 * AGASSVAR(nam,val).eval(ctx) = ctx.scope.assignVariable(nam, val.eval(ctx))
66	 * 
67	 * @return the value assigned to the variable
68	 */
69	public ATObject meta_eval(ATContext ctx) throws InterpreterException {
70		ATObject val = valueExp_.meta_eval(ctx);
71		ctx.base_getLexicalScope().meta_assignVariable(variableName_, val);
72		return val;
73	}
74
75	/**
76	 * AGASSVAR(nam,val).quote(ctx) = AGASSVAR(nam.quote(ctx), val.quote(ctx))
77	 */
78	public ATObject meta_quote(ATContext ctx) throws InterpreterException {
79		return new AGAssignVariable(variableName_.meta_quote(ctx).asSymbol(), valueExp_.meta_quote(ctx).asExpression());
80	}
81	
82	public NATText meta_print() throws InterpreterException {
83		return NATText.atValue(variableName_.meta_print().javaValue + " := " + valueExp_.meta_print().javaValue);
84	}
85    
86    public boolean isVariableAssignment() {
87        return true;
88    }
89    
90    public ATAssignVariable asVariableAssignment() throws XTypeMismatch {
91        return this;
92    }
93}