/interpreter/tags/at2dist090708/src/edu/vub/at/objects/natives/NATTypeTag.java

  1/**
  2 * AmbientTalk/2 Project
  3 * NATTypeTag.java created on 18-feb-2007 at 15:59:20
  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.actors.natives.DiscoveryManager;
 31import edu.vub.at.eval.Evaluator;
 32import edu.vub.at.exceptions.InterpreterException;
 33import edu.vub.at.objects.ATBoolean;
 34import edu.vub.at.objects.ATMethod;
 35import edu.vub.at.objects.ATObject;
 36import edu.vub.at.objects.ATTable;
 37import edu.vub.at.objects.ATTypeTag;
 38import edu.vub.at.objects.coercion.NativeTypeTags;
 39import edu.vub.at.objects.grammar.ATSymbol;
 40import edu.vub.at.objects.mirrors.NativeClosure;
 41import edu.vub.at.objects.natives.grammar.AGSymbol;
 42
 43/**
 44 * The native implementation of AmbientTalk type tag objects.
 45 *
 46 * In principle, care should be taken that all objects implementing the
 47 * type tag interface are isolates, because type tags are usually attributed
 48 * to messages which are isolates themselves.
 49 *
 50 * @author tvcutsem
 51 */
 52public class NATTypeTag extends NATByCopy implements ATTypeTag {
 53
 54	private final ATSymbol typeName_;
 55	private final ATTable parentTypes_;
 56	
 57	public static ATTypeTag[] toTypeTagArray(ATTable types) throws InterpreterException {
 58		if (types == NATTable.EMPTY) {
 59			return NATObject._NO_TYPETAGS_;
 60		}
 61		ATObject[] unwrapped = types.asNativeTable().elements_;
 62		ATTypeTag[] unwrappedTypes = new ATTypeTag[unwrapped.length];
 63		for (int i = 0; i < unwrappedTypes.length; i++) {
 64			unwrappedTypes[i] = unwrapped[i].asTypeTag();
 65		}
 66		return unwrappedTypes;
 67	}
 68	
 69	public static NATTypeTag atValue(String typeName) {
 70		return atValue(AGSymbol.jAlloc(typeName));
 71	}
 72	
 73	public static NATTypeTag atValue(ATSymbol typeName) {
 74		return new NATTypeTag(typeName,
 75				             NATTable.atValue(new ATObject[] { OBJRootType._INSTANCE_ }));
 76	}
 77	
 78	public static NATTypeTag atValue(String typeName, NATTypeTag singleParent) {
 79		return new NATTypeTag(AGSymbol.jAlloc(typeName),
 80				             NATTable.atValue(new ATObject[] { singleParent }));
 81	}
 82	
 83	/**
 84	 * Types should not be created directly because it should be verified
 85	 * that their list of parent types is never empty. Types created
 86	 * with an empty parent list automatically get assigned the root type
 87	 * as their single parent.
 88	 */
 89	public static NATTypeTag atValue(ATSymbol typeName, ATTable parentTypes) {
 90		if (parentTypes == NATTable.EMPTY) {
 91			return new NATTypeTag(typeName, NATTable.atValue(new ATObject[] { OBJRootType._INSTANCE_ }));
 92		} else {
 93			return new NATTypeTag(typeName, parentTypes);
 94		}
 95	}
 96	
 97	/**
 98	 * The constructor is declared protected such that it cannot be used externally,
 99	 * but can be used by the OBJRootType class to create a type with an empty
100	 * parent table, which is normally not allowed. Hence, by construction the only
101	 * type with an empty parent table is the root type. 
102	 */
103	protected NATTypeTag(ATSymbol typeName, ATTable parentTypes) {
104		typeName_ = typeName;
105		parentTypes_ = parentTypes;
106	}
107
108	public ATSymbol base_typeName() throws InterpreterException {
109		return typeName_;
110	}
111
112	public ATTable base_superTypes() throws InterpreterException {
113		return parentTypes_;
114	}
115
116	/**
117	 * Native implementation of:
118	 * 
119	 *	def isSubtypeOf(supertype) {
120	 *		  (supertype.name() == name).or:
121	 *			  { (supertypes.find: { |type|
122	 *				  type.isSubtypeOf(supertype) }) != nil }
123	 *	};
124	 */
125	public ATBoolean base_isSubtypeOf(final ATTypeTag supertype) throws InterpreterException {
126		if (supertype.base_typeName().equals(typeName_)) {
127			return NATBoolean._TRUE_;
128		} else {
129			ATObject found = parentTypes_.base_find_(new NativeClosure(this) {
130				public ATObject base_apply(ATTable args) throws InterpreterException {
131					ATTypeTag type = get(args, 1).asTypeTag();
132					return type.base_isSubtypeOf(supertype);
133				}
134			});
135			return NATBoolean.atValue(found != Evaluator.getNil());
136		}
137	}
138	
139	/**
140	 * By default, annotateMessage is the identity function, it does not add any new metadata
141	 * to the message.
142	 */
143	public ATObject base_annotateMessage(ATObject originalMessage) throws InterpreterException {
144		return originalMessage;
145	}
146	
147	/**
148	 * By default, annotateMethod is the identity function, it does not add any new metadata
149	 * to the method.
150	 */
151	public ATMethod base_annotateMethod(ATMethod originalMethod) throws InterpreterException {
152		return originalMethod;
153	}
154
155	
156	/**
157	 * Identity of types is based on their name
158	 */
159    public ATBoolean base__opeql__opeql_(ATObject comparand) throws InterpreterException {
160    	if (comparand.isTypeTag()) {
161    		return NATBoolean.atValue(comparand.asTypeTag().base_typeName().equals(typeName_));
162    	} else {
163    		return NATBoolean._FALSE_;
164    	}
165    }
166	
167	public boolean isTypeTag() { return true; }
168	
169	public ATTypeTag asTypeTag() { return this; }
170	
171	public NATText meta_print() throws InterpreterException {
172		return NATText.atValue("<type tag:"+typeName_+">");
173	}
174	
175	/**
176	 * Types are singletons
177	 */
178	public ATObject meta_clone() throws InterpreterException {
179		return this;
180	}
181	
182    public ATTable meta_typeTags() throws InterpreterException {
183    	return NATTable.of(NativeTypeTags._TYPETAG_, NativeTypeTags._ISOLATE_);
184    }
185	
186    /** required as type tags are stored in a hashset in the {@link DiscoveryManager} */
187    public int hashCode() { return typeName_.hashCode(); }
188    
189	/**
190	 * The root type of the type hierarchy: every type eventually
191	 * has this type as its parent.
192	 */
193	public static class OBJRootType extends NATTypeTag implements ATTypeTag {
194		
195		private final static AGSymbol _ROOT_NAME_ = AGSymbol.jAlloc("Type");
196		
197		public static final OBJRootType _INSTANCE_ = new OBJRootType();
198		
199		/**
200		 * The root type is named `Type and has no parent types
201		 */
202		private OBJRootType() {
203			super(_ROOT_NAME_, NATTable.EMPTY);
204		}
205
206		/**
207		 * The root type is only a subtype of the root type itself
208		 */
209		public ATBoolean base_isSubtypeOf(ATTypeTag supertype) throws InterpreterException {
210			return NATBoolean.atValue(supertype.base_typeName().equals(_ROOT_NAME_));
211		}
212		
213	}
214	
215}