/interpreter/tags/reactive-pattern-matching/src/edu/vub/at/objects/natives/NATField.java

  1/**
  2 * AmbientTalk/2 Project
  3 * NATField.java created on Jul 27, 2006 at 2:27:53 AM
  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;
 29
 30import edu.vub.at.exceptions.InterpreterException;
 31import edu.vub.at.exceptions.XIllegalOperation;
 32import edu.vub.at.exceptions.XSelectorNotFound;
 33import edu.vub.at.exceptions.XTypeMismatch;
 34import edu.vub.at.objects.ATField;
 35import edu.vub.at.objects.ATMutable;
 36import edu.vub.at.objects.ATObject;
 37import edu.vub.at.objects.ATTable;
 38import edu.vub.at.objects.coercion.NativeTypeTags;
 39import edu.vub.at.objects.grammar.ATSymbol;
 40
 41/**
 42 * NATField implements a causally connected field of an object. Rather than storing
 43 * these fields directly in every object, we choose to only make people pay when they
 44 * choose to reify them. 
 45 * 
 46 * @author smostinc, tvcutsem
 47 */
 48public class NATField extends NATByRef implements ATField, ATMutable {
 49
 50	private final ATSymbol name_;
 51	private final ATObject host_;
 52	
 53	/**
 54	 * Constructs a new native field object linked to the field of a base-level
 55	 * AmbientTalk object
 56	 */
 57	public NATField(ATSymbol name, ATObject host) {
 58		name_ = name;
 59		host_ = host;
 60	}
 61
 62	public ATSymbol base_name() {
 63		return name_;
 64	}
 65
 66	public ATObject base_readField() throws InterpreterException {
 67		try {
 68			return host_.meta_invokeField(host_, name_);
 69		} catch (XSelectorNotFound e) {
 70			e.catchOnlyIfSelectorEquals(name_);
 71			// Since the field was selected from the receiver, it should always be found
 72			throw new XIllegalOperation("Incorrectly initialised field accessed", e);
 73		}
 74	}
 75
 76	public ATObject base_writeField(ATObject newValue) throws InterpreterException {
 77		return host_.impl_invoke(host_, name_.asAssignmentSymbol(), NATTable.of(newValue));
 78	}
 79	
 80	public NATText meta_print() throws InterpreterException {
 81		return NATText.atValue("<field:"+name_.meta_print().javaValue+">");
 82	}
 83	
 84    public boolean isNativeField() {
 85        return true;
 86    }
 87
 88	public ATField asField() throws XTypeMismatch {
 89		return this;
 90	}
 91	
 92	/**
 93	 * Fields can be re-initialized when installed in an object that is being cloned.
 94	 * They expect the new owner of the field as the sole instance to their 'new' method
 95	 */
 96	public ATObject meta_newInstance(ATTable initargs) throws InterpreterException {
 97		if (initargs.base_length() != NATNumber.ONE) {
 98			return super.meta_newInstance(initargs);
 99		} else {
100			ATObject newhost = initargs.base_at(NATNumber.ONE);
101			return new NATField(name_, (NATCallframe) newhost);
102		}
103	}
104	
105    public ATTable meta_typeTags() throws InterpreterException {
106    	return NATTable.of(NativeTypeTags._FIELD_);
107    }
108
109}