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

http://ambienttalk.googlecode.com/
Java | 106 lines | 38 code | 14 blank | 54 comment | 0 complexity | 955f85d2dd2fbb6249604e6c5cde4b09 MD5 | raw file
  1/**
  2 * AmbientTalk/2 Project
  3 * AGUnquoteSplice.java created on 26-jul-2006 at 16:31:07
  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.exceptions.XIllegalQuote;
 32import edu.vub.at.exceptions.XIllegalUnquote;
 33import edu.vub.at.objects.ATContext;
 34import edu.vub.at.objects.ATObject;
 35import edu.vub.at.objects.grammar.ATExpression;
 36import edu.vub.at.objects.grammar.ATUnquoteSplice;
 37import edu.vub.at.objects.natives.NATText;
 38
 39import java.util.Set;
 40
 41/**
 42 * The native implementation of an unquote-splice AG element.
 43 * Example: <tt>#@[1,2,3]</tt>
 44 * 
 45 * @author tvcutsem
 46 */
 47public class AGUnquoteSplice extends AGExpression implements ATUnquoteSplice {
 48
 49	private final ATExpression uqsExp_;
 50	
 51	public AGUnquoteSplice(ATExpression exp) {
 52		uqsExp_ = exp;
 53	}
 54	
 55	public ATExpression base_expression() { return uqsExp_; }
 56
 57	/**
 58	 * An unquotation cannot be evaluated, but rather gives rise to an XIllegalUnquote exception.
 59	 * This is because an unquotation should always be nested within a quotation.
 60	 * 
 61	 * AGUQS(exp).eval(ctx) = ERROR
 62	 */
 63	public ATObject meta_eval(ATContext ctx) throws InterpreterException {
 64		throw new XIllegalUnquote(uqsExp_);
 65	}
 66
 67	/**
 68	 * Quoting a spliced unquotation means evaluating its contained expression, and returning
 69	 * its value as the result of the quote. A spliced unquotation can normally only
 70	 * be invoked where a table or begin is expected. The resulting table is replaced by the result of
 71	 * evaluating the unquote-splice's encapsulated expression.
 72	 * 
 73	 * It is the table's responsibility to query an AGUnquoteSplice element for its expression and deal with the inlining appropriately.
 74	 */
 75	public ATObject meta_quote(ATContext ctx) throws InterpreterException {
 76		throw new XIllegalQuote(uqsExp_.meta_print().javaValue);
 77	}
 78	
 79	public NATText meta_print() throws InterpreterException {
 80		return NATText.atValue("#@("+ uqsExp_.meta_print().javaValue + ")");
 81	}
 82	
 83	public boolean isUnquoteSplice() {
 84		return true;
 85	}
 86	
 87	public ATUnquoteSplice asUnquoteSplice() {
 88		return this;
 89	}
 90	
 91	/**
 92	 * FV(#@exp) = FV(exp)
 93	 */
 94	public Set impl_freeVariables() throws InterpreterException {
 95		return uqsExp_.impl_freeVariables();
 96	}
 97	
 98	/**
 99	 * Turn unquotation back into quotation.
100	 * E.g. `(x + #@y) => y is considered a free variable.
101	 */
102	public Set impl_quotedFreeVariables() throws InterpreterException {
103		return this.impl_freeVariables();
104	}
105
106}