/interpreter/tags/at2dist220411/src/edu/vub/at/objects/natives/grammar/AGQuote.java

  1/**
  2 * AmbientTalk/2 Project
  3 * AGQuote.java created on 26-jul-2006 at 16:26:41
  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.ATQuote;
 34import edu.vub.at.objects.grammar.ATStatement;
 35import edu.vub.at.objects.natives.NATText;
 36import edu.vub.util.TempFieldGenerator;
 37
 38import java.util.HashSet;
 39import java.util.Set;
 40
 41/**
 42 * @author tvc
 43 *
 44 * The native implementation of a quotation AG element.
 45 */
 46public final class AGQuote extends AGExpression implements ATQuote {
 47
 48	private final ATStatement stmt_;
 49	
 50	public AGQuote(ATStatement stmt) {
 51		stmt_ = stmt;
 52	}
 53	
 54	public ATStatement base_statement() { return stmt_; }
 55
 56	/**
 57	 * To evaluate a quotation, start quoting its contained statement.
 58	 * This recursive quoting is necessary in order to properly unquote nested unquotations.
 59	 * 
 60	 * AGQUO(stmt).eval(ctx) = stmt.quote(ctx)
 61	 * 
 62	 * @return the quoted statement
 63	 */
 64	public ATObject meta_eval(ATContext ctx) throws InterpreterException {
 65		return stmt_.meta_quote(ctx);
 66	}
 67
 68	/**
 69	 * Quoting a quotation results in a bare quotation, where quotations and unquotations are left unexpanded.
 70	 */
 71	public ATObject meta_quote(ATContext ctx) throws InterpreterException {
 72		return this;
 73	}
 74	
 75	public NATText meta_print() throws InterpreterException {
 76		return NATText.atValue("`("+ stmt_.meta_print().javaValue + ")");
 77	}
 78	
 79	public NATText impl_asUnquotedCode(TempFieldGenerator objectMap) throws InterpreterException {
 80		objectMap.incQuoteLevel();
 81		NATText code = NATText.atValue("`("+ stmt_.impl_asUnquotedCode(objectMap).javaValue + ")");
 82		objectMap.decQuoteLevel();
 83		return code;
 84	}
 85	
 86	public ATQuote asQuote() throws InterpreterException {
 87		return this;
 88	}
 89	
 90	/**
 91	 * FV(`exp) = FV_in_unquoted_expressions(exp)
 92	 */
 93	public Set impl_freeVariables() throws InterpreterException {
 94		return stmt_.impl_quotedFreeVariables();
 95	}
 96	
 97	/**
 98	 * The expression `( `(x + #(y)) ) has no free variables.
 99	 * It is assumed that the inner quotation is returned bare (without expansion)
100	 */
101	public Set impl_quotedFreeVariables() throws InterpreterException {
102		return new HashSet();
103	}
104
105}