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

  1/**
  2 * AmbientTalk/2 Project
  3 * AGDefFunction.java created on 26-jul-2006 at 15:44:08
  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.eval.Evaluator;
 31import edu.vub.at.exceptions.InterpreterException;
 32import edu.vub.at.objects.ATContext;
 33import edu.vub.at.objects.ATObject;
 34import edu.vub.at.objects.ATTable;
 35import edu.vub.at.objects.grammar.ATBegin;
 36import edu.vub.at.objects.grammar.ATDefMethod;
 37import edu.vub.at.objects.grammar.ATSymbol;
 38import edu.vub.at.objects.natives.NATClosure;
 39import edu.vub.at.objects.natives.NATMethod;
 40import edu.vub.at.objects.natives.NATText;
 41
 42/**
 43 * The native implementation of a function definition abstract grammar element.
 44 * This AG element covers both method and closure definition.
 45 * 
 46 * @author tvc
 47 */
 48public final class AGDefFunction extends NATAbstractGrammar implements ATDefMethod {
 49
 50	private final ATSymbol selectorExp_;
 51	private final ATTable argumentExps_;
 52	private final ATBegin bodyStmts_;
 53	
 54	public AGDefFunction(ATSymbol sel, ATTable args, ATBegin bdy) {
 55		selectorExp_ = sel;
 56		argumentExps_ = args;
 57		bodyStmts_ = bdy;
 58	}
 59	
 60	public ATSymbol base_getSelector() {
 61		return selectorExp_;
 62	}
 63
 64	public ATTable base_getArguments() {
 65		return argumentExps_;
 66	}
 67
 68	public ATBegin base_getBodyExpression() {
 69		return bodyStmts_;
 70	}
 71
 72	/**
 73	 * Defines a new function (method or closure) in the current scope.
 74	 * If a function definition is executed in the context of an object,
 75	 * a new method is created. If, however, the function definition
 76	 * is executed in the context of a call frame (i.e. its definition
 77	 * is nested within a method/function) then a closure is created instead.
 78	 * 
 79	 * The return value of a function definition is always a closure encapsulating the function.
 80	 * 
 81	 * AGDEFFUN(nam,par,bdy).eval(ctx) =
 82	 *   if ctx.scope.isCallFrame
 83	 *      ctx.scope.defineField(nam, AGCLO(AGMTH(nam,par,bdy), ctx))
 84	 *   else
 85	 *      ctx.scope.addMethod(nam, AGMTH(nam,par,bdy))
 86	 * 
 87	 */
 88	public ATObject meta_eval(ATContext ctx) throws InterpreterException {
 89		ATObject current = ctx.base_getLexicalScope();
 90		if (current.isCallFrame()) {
 91			NATClosure clo = new NATClosure(new NATMethod(selectorExp_, argumentExps_, bodyStmts_), ctx);
 92			current.meta_defineField(selectorExp_, clo);
 93			return clo;
 94		} else {
 95			current.meta_addMethod(new NATMethod(selectorExp_, argumentExps_, bodyStmts_));
 96			return current.meta_select(current, selectorExp_);
 97		}
 98	}
 99
100	/**
101	 * Quoting a function definition results in a new quoted function definition.
102	 * 
103	 * AGDEFFUN(nam,par,bdy).quote(ctx) = AGDEFFUN(nam.quote(ctx), par.quote(ctx), bdy.quote(ctx))
104	 */
105	public ATObject meta_quote(ATContext ctx) throws InterpreterException {
106		return new AGDefFunction(selectorExp_.meta_quote(ctx).asSymbol(),
107				              argumentExps_.meta_quote(ctx).asTable(),
108				              bodyStmts_.meta_quote(ctx).asBegin());
109	}
110	
111	public NATText meta_print() throws InterpreterException {
112		return NATText.atValue("def " +
113				selectorExp_.meta_print().javaValue +
114				Evaluator.printAsList(argumentExps_).javaValue +
115				" { " + bodyStmts_.meta_print().javaValue + " }");
116	}
117
118}