/interpreter/tags/at2dist041108/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.ATDefinition;
 35import edu.vub.at.objects.grammar.ATExpression;
 36import edu.vub.at.objects.grammar.ATSymbol;
 37import edu.vub.at.objects.natives.NATText;
 38
 39import java.util.HashSet;
 40import java.util.Set;
 41
 42/**
 43 * @author tvc
 44 *
 45 * AGDefField represents the abstract grammar for defining fields.
 46 * Examples:
 47 *   <tt>x := 5</tt>
 48 *   <tt>+ := "foo"</tt>
 49 */
 50public final class AGDefField extends AGDefinition implements ATDefField {
 51
 52	private final ATSymbol name_;
 53	private final ATExpression valueExp_;
 54	
 55	public AGDefField(ATSymbol name, ATExpression value) {
 56		name_ = name;
 57		valueExp_ = value;
 58	}
 59	
 60	public ATSymbol base_name() { return name_; }
 61	public ATExpression base_valueExpression() { return valueExp_; }
 62	
 63	/**
 64	 * Defines a new field in the current scope. The return value is
 65	 * the evaluated value.
 66	 * 
 67	 * AGDEFFIELD(nam,val).eval(ctx) =
 68	 *   ctx.scope.addField(nam, val.eval(ctx))
 69	 */
 70	public ATObject meta_eval(ATContext ctx) throws InterpreterException {
 71		ATObject val = valueExp_.meta_eval(ctx);
 72		ctx.base_lexicalScope().meta_defineField(name_, val);
 73		return val;
 74	}
 75
 76	/**
 77	 * Quoting a field definition results in a new quoted field definition.
 78	 * 
 79	 * AGDEFFIELD(nam,val).quote(ctx) = AGDEFFIELD(nam.quote(ctx), val.quote(ctx))
 80	 */
 81	public ATObject meta_quote(ATContext ctx) throws InterpreterException {
 82		return new AGDefField(name_.meta_quote(ctx).asSymbol(), valueExp_.meta_quote(ctx).asExpression());
 83	}
 84	
 85	public NATText meta_print() throws InterpreterException {
 86		return NATText.atValue("def " + name_.meta_print().javaValue + " := " + valueExp_.meta_print().javaValue);
 87	}
 88	
 89	/**
 90	 * IV(def x := val) = { x }
 91	 */
 92	public Set impl_introducedVariables() throws InterpreterException {
 93		HashSet singleton = new HashSet();
 94		singleton.add(name_);
 95		return singleton;
 96	}
 97	
 98	/**
 99	 * FV(def var := exp) = FV(exp) \ { var }
100	 */
101	public Set impl_freeVariables() throws InterpreterException {
102		Set fvValueExp = valueExp_.impl_freeVariables();
103		fvValueExp.remove(name_);
104		return fvValueExp;
105	}
106	
107	
108	public Set impl_quotedFreeVariables() throws InterpreterException {
109		Set qfv = valueExp_.impl_quotedFreeVariables();
110		qfv.addAll(name_.impl_quotedFreeVariables());
111		return qfv;
112	}
113
114}