/interpreter/tags/at2dist130208/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.exceptions.InterpreterException;
 32import edu.vub.at.objects.ATBoolean;
 33import edu.vub.at.objects.ATObject;
 34import edu.vub.at.objects.ATTable;
 35import edu.vub.at.objects.ATTypeTag;
 36import edu.vub.at.objects.coercion.NativeTypeTags;
 37import edu.vub.at.objects.grammar.ATSymbol;
 38import edu.vub.at.objects.mirrors.NativeClosure;
 39import edu.vub.at.objects.natives.grammar.AGSymbol;
 40
 41/**
 42 * The native implementation of AmbientTalk type tag objects.
 43 *
 44 * In principle, care should be taken that all objects implementing the
 45 * type tag interface are isolates, because type tags are usually attributed
 46 * to messages which are isolates themselves.
 47 *
 48 * @author tvcutsem
 49 */
 50public class NATTypeTag extends NATByCopy implements ATTypeTag {
 51
 52	private final ATSymbol typeName_;
 53	private final ATTable parentTypes_;
 54	
 55	public static ATTypeTag[] toTypeTagArray(ATTable types) throws InterpreterException {
 56		if (types == NATTable.EMPTY) {
 57			return NATObject._NO_TYPETAGS_;
 58		}
 59		ATObject[] unwrapped = types.asNativeTable().elements_;
 60		ATTypeTag[] unwrappedTypes = new ATTypeTag[unwrapped.length];
 61		for (int i = 0; i < unwrappedTypes.length; i++) {
 62			unwrappedTypes[i] = unwrapped[i].asTypeTag();
 63		}
 64		return unwrappedTypes;
 65	}
 66	
 67	public static NATTypeTag atValue(String typeName) {
 68		return atValue(AGSymbol.jAlloc(typeName));
 69	}
 70	
 71	public static NATTypeTag atValue(ATSymbol typeName) {
 72		return new NATTypeTag(typeName,
 73				             NATTable.atValue(new ATObject[] { OBJRootType._INSTANCE_ }));
 74	}
 75	
 76	public static NATTypeTag atValue(String typeName, NATTypeTag singleParent) {
 77		return new NATTypeTag(AGSymbol.jAlloc(typeName),
 78				             NATTable.atValue(new ATObject[] { singleParent }));
 79	}
 80	
 81	/**
 82	 * Types should not be created directly because it should be verified
 83	 * that their list of parent types is never empty. Types created
 84	 * with an empty parent list automatically get assigned the root type
 85	 * as their single parent.
 86	 */
 87	public static NATTypeTag atValue(ATSymbol typeName, ATTable parentTypes) {
 88		if (parentTypes == NATTable.EMPTY) {
 89			return new NATTypeTag(typeName, NATTable.atValue(new ATObject[] { OBJRootType._INSTANCE_ }));
 90		} else {
 91			return new NATTypeTag(typeName, parentTypes);
 92		}
 93	}
 94	
 95	/**
 96	 * The constructor is declared protected such that it cannot be used externally,
 97	 * but can be used by the OBJRootType class to create a type with an empty
 98	 * parent table, which is normally not allowed. Hence, by construction the only
 99	 * type with an empty parent table is the root type. 
100	 */
101	protected NATTypeTag(ATSymbol typeName, ATTable parentTypes) {
102		typeName_ = typeName;
103		parentTypes_ = parentTypes;
104	}
105
106	public ATSymbol base_typeName() throws InterpreterException {
107		return typeName_;
108	}
109
110	public ATTable base_superTypes() throws InterpreterException {
111		return parentTypes_;
112	}
113
114	/**
115	 * Native implementation of:
116	 * 
117	 *	def isSubtypeOf(supertype) {
118	 *		  (supertype.name() == name).or:
119	 *			  { (supertypes.find: { |type|
120	 *				  type.isSubtypeOf(supertype) }) != nil }
121	 *	};
122	 */
123	public ATBoolean base_isSubtypeOf(final ATTypeTag supertype) throws InterpreterException {
124		if (supertype.base_typeName().equals(typeName_)) {
125			return NATBoolean._TRUE_;
126		} else {
127			ATObject found = parentTypes_.base_find_(new NativeClosure(this) {
128				public ATObject base_apply(ATTable args) throws InterpreterException {
129					ATTypeTag type = get(args, 1).asTypeTag();
130					return type.base_isSubtypeOf(supertype);
131				}
132			});
133			return NATBoolean.atValue(found != OBJNil._INSTANCE_);
134		}
135	}
136	
137	/**
138	 * Identity of types is based on their name
139	 */
140    public ATBoolean base__opeql__opeql_(ATObject comparand) throws InterpreterException {
141    	if (comparand.isTypeTag()) {
142    		return comparand.asTypeTag().base_typeName().base__opeql__opeql_(typeName_);
143    	} else {
144    		return NATBoolean._FALSE_;
145    	}
146    }
147	
148	public boolean isTypeTag() { return true; }
149	
150	public ATTypeTag asTypeTag() { return this; }
151	
152	public NATText meta_print() throws InterpreterException {
153		return NATText.atValue("<type tag:"+typeName_+">");
154	}
155	
156	/**
157	 * Types are singletons
158	 */
159	public ATObject meta_clone() throws InterpreterException {
160		return this;
161	}
162	
163    public ATTable meta_typeTags() throws InterpreterException {
164    	return NATTable.of(NativeTypeTags._TYPETAG_, NativeTypeTags._ISOLATE_);
165    }
166	
167    /** required as type tags are stored in a hashset in the {@link DiscoveryManager} */
168    public int hashCode() { return typeName_.hashCode(); }
169    
170	/**
171	 * The root type of the type hierarchy: every type eventually
172	 * has this type as its parent.
173	 */
174	public static class OBJRootType extends NATTypeTag implements ATTypeTag {
175		
176		private final static AGSymbol _ROOT_NAME_ = AGSymbol.jAlloc("Type");
177		
178		public static final OBJRootType _INSTANCE_ = new OBJRootType();
179		
180		/**
181		 * The root type is named `Type and has no parent types
182		 */
183		private OBJRootType() {
184			super(_ROOT_NAME_, NATTable.EMPTY);
185		}
186
187		/**
188		 * The root type is only a subtype of the root type itself
189		 */
190		public ATBoolean base_isSubtypeOf(ATTypeTag supertype) throws InterpreterException {
191			return NATBoolean.atValue(supertype.base_typeName().equals(_ROOT_NAME_));
192		}
193		
194	}
195	
196}