/interpreter/tags/at2-build190607/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.coercion.NativeTypeTags;
 36import edu.vub.at.objects.grammar.ATBegin;
 37import edu.vub.at.objects.grammar.ATDefMethod;
 38import edu.vub.at.objects.grammar.ATSymbol;
 39import edu.vub.at.objects.natives.NATClosure;
 40import edu.vub.at.objects.natives.NATMethod;
 41import edu.vub.at.objects.natives.NATTable;
 42import edu.vub.at.objects.natives.NATText;
 43
 44/**
 45 * The native implementation of a function definition abstract grammar element.
 46 * This AG element covers both method and closure definition.
 47 * 
 48 * @author tvc
 49 */
 50public final class AGDefFunction extends NATAbstractGrammar implements ATDefMethod {
 51
 52	private final ATSymbol selectorExp_;
 53	private final ATTable argumentExps_;
 54	private final ATBegin bodyStmts_;
 55	
 56	private NATMethod preprocessedMethod_;
 57	
 58	public AGDefFunction(ATSymbol sel, ATTable args, ATBegin bdy) throws InterpreterException {
 59		selectorExp_ = sel;
 60		argumentExps_ = args;
 61		bodyStmts_ = bdy;
 62	}
 63	
 64	public ATSymbol base_getSelector() {
 65		return selectorExp_;
 66	}
 67
 68	public ATTable base_getArguments() {
 69		return argumentExps_;
 70	}
 71
 72	public ATBegin base_getBodyExpression() {
 73		return bodyStmts_;
 74	}
 75	
 76	/**
 77	 * Defines a new function (method or closure) in the current scope.
 78	 * If a function definition is executed in the context of an object,
 79	 * a new method is created. If, however, the function definition
 80	 * is executed in the context of a call frame (i.e. its definition
 81	 * is nested within a method/function) then a closure is created instead.
 82	 * 
 83	 * The return value of a function definition is always a closure encapsulating the function.
 84	 * 
 85	 * AGDEFFUN(nam,par,bdy).eval(ctx) =
 86	 *   if ctx.scope.isCallFrame
 87	 *      ctx.scope.defineField(nam, AGCLO(AGMTH(nam,par,bdy), ctx))
 88	 *   else
 89	 *      ctx.scope.addMethod(nam, AGMTH(nam,par,bdy))
 90	 * 
 91	 */
 92	public ATObject meta_eval(ATContext ctx) throws InterpreterException {
 93		// the method is not yet created in the constructor because this gives problems
 94		// with quoted parameters: a quoted parameter would result in an illegal parameter
 95		// exception while actually the function was defined in the context of a quotation,
 96		// so at runtime the function definition would have never been evaluated (but quoted instead)
 97		if (preprocessedMethod_ == null) {
 98			preprocessedMethod_ = new NATMethod(selectorExp_, argumentExps_, bodyStmts_);
 99		}
100		
101		ATObject current = ctx.base_getLexicalScope();
102		if (current.isCallFrame()) {
103			NATClosure clo = new NATClosure(preprocessedMethod_, ctx);
104			current.meta_defineField(selectorExp_, clo);
105			return clo;
106		} else {
107			current.meta_addMethod(preprocessedMethod_);
108			return current.meta_select(current, selectorExp_);
109		}
110	}
111
112	/**
113	 * Quoting a function definition results in a new quoted function definition.
114	 * 
115	 * AGDEFFUN(nam,par,bdy).quote(ctx) = AGDEFFUN(nam.quote(ctx), par.quote(ctx), bdy.quote(ctx))
116	 */
117	public ATObject meta_quote(ATContext ctx) throws InterpreterException {
118		return new AGDefFunction(selectorExp_.meta_quote(ctx).asSymbol(),
119				                 argumentExps_.meta_quote(ctx).asTable(),
120				                 bodyStmts_.meta_quote(ctx).asBegin());
121	}
122	
123	public NATText meta_print() throws InterpreterException {
124		return NATText.atValue("def " +
125				selectorExp_.meta_print().javaValue +
126				Evaluator.printAsList(argumentExps_).javaValue +
127				" { " + bodyStmts_.meta_print().javaValue + " }");
128	}
129	
130    public ATTable meta_getTypeTags() throws InterpreterException {
131    	return NATTable.of(NativeTypeTags._METHOD_DEFINITION_);
132    }
133
134}