/interpreter/tags/at2dist170907/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.exceptions.InterpreterException;
 31import edu.vub.at.objects.ATBoolean;
 32import edu.vub.at.objects.ATObject;
 33import edu.vub.at.objects.ATTable;
 34import edu.vub.at.objects.ATTypeTag;
 35import edu.vub.at.objects.coercion.NativeTypeTags;
 36import edu.vub.at.objects.grammar.ATSymbol;
 37import edu.vub.at.objects.mirrors.NativeClosure;
 38import edu.vub.at.objects.natives.grammar.AGSymbol;
 39
 40/**
 41 * The native implementation of AmbientTalk type tag objects.
 42 *
 43 * In principle, care should be taken that all objects implementing the
 44 * type tag interface are isolates, because type tags are usually attributed
 45 * to messages which are isolates themselves.
 46 *
 47 * @author tvcutsem
 48 */
 49public class NATTypeTag extends NATByCopy implements ATTypeTag {
 50
 51	private final ATSymbol typeName_;
 52	private final ATTable parentTypes_;
 53	
 54	public static ATTypeTag[] toTypeTagArray(ATTable types) throws InterpreterException {
 55		if (types == NATTable.EMPTY) {
 56			return NATObject._NO_TYPETAGS_;
 57		}
 58		ATObject[] unwrapped = types.asNativeTable().elements_;
 59		ATTypeTag[] unwrappedTypes = new ATTypeTag[unwrapped.length];
 60		for (int i = 0; i < unwrappedTypes.length; i++) {
 61			unwrappedTypes[i] = unwrapped[i].asTypeTag();
 62		}
 63		return unwrappedTypes;
 64	}
 65	
 66	public static NATTypeTag atValue(String typeName) {
 67		return atValue(AGSymbol.jAlloc(typeName));
 68	}
 69	
 70	public static NATTypeTag atValue(ATSymbol typeName) {
 71		return new NATTypeTag(typeName,
 72				             NATTable.atValue(new ATObject[] { OBJRootType._INSTANCE_ }));
 73	}
 74	
 75	public static NATTypeTag atValue(String typeName, NATTypeTag singleParent) {
 76		return new NATTypeTag(AGSymbol.jAlloc(typeName),
 77				             NATTable.atValue(new ATObject[] { singleParent }));
 78	}
 79	
 80	/**
 81	 * Types should not be created directly because it should be verified
 82	 * that their list of parent types is never empty. Types created
 83	 * with an empty parent list automatically get assigned the root type
 84	 * as their single parent.
 85	 */
 86	public static NATTypeTag atValue(ATSymbol typeName, ATTable parentTypes) {
 87		if (parentTypes == NATTable.EMPTY) {
 88			return new NATTypeTag(typeName, NATTable.atValue(new ATObject[] { OBJRootType._INSTANCE_ }));
 89		} else {
 90			return new NATTypeTag(typeName, parentTypes);
 91		}
 92	}
 93	
 94	/**
 95	 * The constructor is declared protected such that it cannot be used externally,
 96	 * but can be used by the OBJRootType class to create a type with an empty
 97	 * parent table, which is normally not allowed. Hence, by construction the only
 98	 * type with an empty parent table is the root type. 
 99	 */
100	protected NATTypeTag(ATSymbol typeName, ATTable parentTypes) {
101		typeName_ = typeName;
102		parentTypes_ = parentTypes;
103	}
104
105	public ATSymbol base_typeName() throws InterpreterException {
106		return typeName_;
107	}
108
109	public ATTable base_superTypes() throws InterpreterException {
110		return parentTypes_;
111	}
112
113	/**
114	 * Native implementation of:
115	 * 
116	 *	def isSubtypeOf(supertype) {
117	 *		  (supertype.name() == name).or:
118	 *			  { (supertypes.find: { |type|
119	 *				  type.isSubtypeOf(supertype) }) != nil }
120	 *	};
121	 */
122	public ATBoolean base_isSubtypeOf(final ATTypeTag supertype) throws InterpreterException {
123		if (supertype.base_typeName().equals(typeName_)) {
124			return NATBoolean._TRUE_;
125		} else {
126			ATObject found = parentTypes_.base_find_(new NativeClosure(this) {
127				public ATObject base_apply(ATTable args) throws InterpreterException {
128					ATTypeTag type = get(args, 1).asTypeTag();
129					return type.base_isSubtypeOf(supertype);
130				}
131			});
132			return NATBoolean.atValue(found != OBJNil._INSTANCE_);
133		}
134	}
135	
136	/**
137	 * Identity of types is based on their name
138	 */
139    public ATBoolean base__opeql__opeql_(ATObject comparand) throws InterpreterException {
140    	if (comparand.isTypeTag()) {
141    		return comparand.asTypeTag().base_typeName().base__opeql__opeql_(typeName_);
142    	} else {
143    		return NATBoolean._FALSE_;
144    	}
145    }
146	
147	public boolean isTypeTag() { return true; }
148	
149	public ATTypeTag asTypeTag() { return this; }
150	
151	public NATText meta_print() throws InterpreterException {
152		return NATText.atValue("<type tag:"+typeName_+">");
153	}
154	
155	/**
156	 * Types are singletons
157	 */
158	public ATObject meta_clone() throws InterpreterException {
159		return this;
160	}
161	
162    public ATTable meta_typeTags() throws InterpreterException {
163    	return NATTable.of(NativeTypeTags._TYPETAG_, NativeTypeTags._ISOLATE_);
164    }
165	
166	/**
167	 * The root type of the type hierarchy: every type eventually
168	 * has this type as its parent.
169	 */
170	public static class OBJRootType extends NATTypeTag implements ATTypeTag {
171		
172		private final static AGSymbol _ROOT_NAME_ = AGSymbol.jAlloc("Type");
173		
174		public static final OBJRootType _INSTANCE_ = new OBJRootType();
175		
176		/**
177		 * The root type is named `Type and has no parent types
178		 */
179		private OBJRootType() {
180			super(_ROOT_NAME_, NATTable.EMPTY);
181		}
182
183		/**
184		 * The root type is only a subtype of the root type itself
185		 */
186		public ATBoolean base_isSubtypeOf(ATTypeTag supertype) throws InterpreterException {
187			return NATBoolean.atValue(supertype.base_typeName().equals(_ROOT_NAME_));
188		}
189		
190	}
191	
192}