/interpreter/tags/at2dist041108/src/edu/vub/at/objects/natives/grammar/AGAssignmentSymbol.java

  1/**
  2 * AmbientTalk/2 Project
  3 * AGAssignmentSymbol.java created on 2-jul-2007 at 13:45:32
  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.XIllegalOperation;
 32import edu.vub.at.objects.ATContext;
 33import edu.vub.at.objects.ATObject;
 34import edu.vub.at.objects.ATText;
 35import edu.vub.at.objects.grammar.ATAssignmentSymbol;
 36import edu.vub.at.objects.grammar.ATSymbol;
 37import edu.vub.at.objects.natives.NATText;
 38
 39/**
 40 * An assignment symbol is created by suffixing an ordinary symbol with a :=. It can be created 
 41 * explicitly through qutoting and is created when assigning a field at base-level to map such
 42 * assignments onto a method invocation. Also it can be created when explicitly defining accessor 
 43 * methods.
 44 * 
 45 * @author smostinc
 46 */
 47public class AGAssignmentSymbol extends AGSymbol implements ATAssignmentSymbol {
 48
 49	/**
 50	 * @param name a string with a ':=' suffix
 51	 */
 52	public static AGSymbol jAlloc(String name) {
 53		synchronized (_STRINGPOOL_) {
 54			AGSymbol existing = (AGSymbol) _STRINGPOOL_.get(name);
 55			if (existing == null) {
 56				existing = new AGAssignmentSymbol(name);
 57				_STRINGPOOL_.put(name, existing);
 58			}
 59			return existing;	
 60		}
 61	}
 62	
 63	protected AGAssignmentSymbol(String txt) {
 64		// cut the := part of the symbol name, e.g. foo:= -> foo
 65		super(txt.substring(0,txt.length()-2));
 66	}
 67
 68	public boolean isAssignmentSymbol() {
 69		return true;
 70	}
 71	
 72	public AGAssignmentSymbol asAssignmentSymbol() {
 73		return this;
 74	}
 75	
 76	public ATText base_text() {
 77		return NATText.atValue(toString());
 78	}
 79
 80	/**
 81	 * It is illegal to evaluate an assignment symbol in base-level code
 82	 */
 83	public ATObject meta_eval(ATContext ctx) throws InterpreterException {
 84		throw new XIllegalOperation("Cannot evaluate an assignment symbol as an ordinary symbol");
 85	}
 86
 87	public NATText meta_print() {
 88		return NATText.atValue(toString());
 89	}
 90
 91	public ATObject meta_resolve() throws InterpreterException {
 92		return AGAssignmentSymbol.jAlloc(toString());
 93	}
 94
 95	public String toString() {
 96		return super.toString() + ":=";
 97	}
 98	
 99	/**
100	 * @return the field name being assigned by this assignment symbol
101	 */
102	public ATSymbol base_fieldName() {
103		return AGSymbol.jAlloc(super.toString());
104	}
105	
106}