/interpreter/tags/at2dist091109/src/edu/vub/at/objects/natives/grammar/AGTabulation.java

  1/**
  2 * AmbientTalk/2 Project
  3 * AGTabulation.java created on 26-jul-2006 at 16:19:54
  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.ATExpression;
 34import edu.vub.at.objects.grammar.ATTabulation;
 35import edu.vub.at.objects.natives.NATMethodInvocation;
 36import edu.vub.at.objects.natives.NATTable;
 37import edu.vub.at.objects.natives.NATText;
 38
 39import java.util.Set;
 40
 41/**
 42 * The native implementation of a tabulation AG element.
 43 * Example: <tt>(o.tab)[x+1]</tt>
 44 * 
 45 * @author tvcutsem
 46 */
 47public final class AGTabulation extends AGExpression implements ATTabulation {
 48
 49	private final ATExpression tblExp_;
 50	private final ATExpression idxExp_;
 51	
 52	public AGTabulation(ATExpression tbl, ATExpression idx) {
 53		tblExp_ = tbl;
 54		idxExp_ = idx;
 55	}
 56	
 57	public ATExpression base_tableExpression() { return tblExp_; }
 58
 59	public ATExpression base_indexExpression() { return idxExp_; }
 60
 61	/**
 62	 * To evaluate a tabulation, evaluate the tabulation expression to a table,
 63	 * evaluate the index expression into a valid index, and then access the table at the given index slot.
 64	 * 
 65	 * AGTBL(tbl,idx).eval(ctx) = tbl.eval(ctx).at(idx.eval(ctx))
 66	 * 
 67	 * @return the value of the indexed table slot.
 68	 */
 69	public ATObject meta_eval(ATContext ctx) throws InterpreterException {
 70		ATObject col = tblExp_.meta_eval(ctx);
 71		ATObject idx = idxExp_.meta_eval(ctx);
 72
 73		return col.meta_invoke(col, 
 74				new NATMethodInvocation(
 75						AGSymbol.jAlloc("at"), 
 76						NATTable.of(idx),
 77						NATTable.EMPTY));
 78	}
 79
 80	/**
 81	 * Quoting a tabulation results in a new quoted tabulation
 82	 * 
 83	 * AGTBL(tbl,idx).quote(ctx) = AGTBL(tbl.quote(ctx),idx.quote(ctx))
 84	 */
 85	public ATObject meta_quote(ATContext ctx) throws InterpreterException {
 86		return new AGTabulation(tblExp_.meta_quote(ctx).asExpression(),
 87				               idxExp_.meta_quote(ctx).asExpression());
 88	}
 89	
 90	public NATText meta_print() throws InterpreterException {
 91		return NATText.atValue(tblExp_.meta_print().javaValue + "[" +
 92				              idxExp_.meta_print().javaValue + "]");
 93	}
 94	
 95	/**
 96	 * FV(tblExp[idxExp]) = FV(tblExp) U FV(idxExp)
 97	 */
 98	public Set impl_freeVariables() throws InterpreterException {
 99		Set fvTblExp = tblExp_.impl_freeVariables();
100		fvTblExp.addAll(idxExp_.impl_freeVariables());
101		return fvTblExp;
102	}
103	
104	
105	public Set impl_quotedFreeVariables() throws InterpreterException {
106		Set qfv = tblExp_.impl_quotedFreeVariables();
107		qfv.addAll(idxExp_.impl_quotedFreeVariables());
108		return qfv;
109	}
110	
111}