/interpreter/tags/at2dist220411/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;
 38import edu.vub.util.TempFieldGenerator;
 39
 40/**
 41 * An assignment symbol is created by suffixing an ordinary symbol with a :=. It can be created 
 42 * explicitly through qutoting and is created when assigning a field at base-level to map such
 43 * assignments onto a method invocation. Also it can be created when explicitly defining accessor 
 44 * methods.
 45 * 
 46 * @author smostinc
 47 */
 48public class AGAssignmentSymbol extends AGSymbol implements ATAssignmentSymbol {
 49
 50	/**
 51	 * @param name a string with a ':=' suffix
 52	 */
 53	public static AGSymbol jAlloc(String name) {
 54		synchronized (_STRINGPOOL_) {
 55			AGSymbol existing = (AGSymbol) _STRINGPOOL_.get(name);
 56			if (existing == null) {
 57				existing = new AGAssignmentSymbol(name);
 58				_STRINGPOOL_.put(name, existing);
 59			}
 60			return existing;	
 61		}
 62	}
 63	
 64	protected AGAssignmentSymbol(String txt) {
 65		// cut the := part of the symbol name, e.g. foo:= -> foo
 66		super(txt.substring(0,txt.length()-2));
 67	}
 68
 69	public boolean isAssignmentSymbol() {
 70		return true;
 71	}
 72	
 73	public AGAssignmentSymbol asAssignmentSymbol() {
 74		return this;
 75	}
 76	
 77	public ATText base_text() {
 78		return NATText.atValue(toString());
 79	}
 80
 81	/**
 82	 * It is illegal to evaluate an assignment symbol in base-level code
 83	 */
 84	public ATObject meta_eval(ATContext ctx) throws InterpreterException {
 85		throw new XIllegalOperation("Cannot evaluate an assignment symbol as an ordinary symbol");
 86	}
 87
 88	public NATText meta_print() {
 89		return NATText.atValue(toString());
 90	}
 91	
 92	public NATText impl_asCode(TempFieldGenerator objectMap) throws InterpreterException {
 93		return NATText.atValue(toString());
 94	}
 95
 96	public ATObject meta_resolve() throws InterpreterException {
 97		return AGAssignmentSymbol.jAlloc(toString());
 98	}
 99
100	public String toString() {
101		return super.toString() + ":=";
102	}
103	
104	/**
105	 * @return the field name being assigned by this assignment symbol
106	 */
107	public ATSymbol base_fieldName() {
108		return AGSymbol.jAlloc(super.toString());
109	}
110	
111}