/interpreter/tags/at2-build190607/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 * @author tvcutsem
 44 */
 45public class NATTypeTag extends NATByCopy implements ATTypeTag {
 46
 47	private final ATSymbol typeName_;
 48	private final ATTable parentTypes_;
 49	
 50	public static ATTypeTag[] toTypeTagArray(ATTable types) throws InterpreterException {
 51		if (types == NATTable.EMPTY) {
 52			return NATObject._NO_TYPETAGS_;
 53		}
 54		ATObject[] unwrapped = types.asNativeTable().elements_;
 55		ATTypeTag[] unwrappedTypes = new ATTypeTag[unwrapped.length];
 56		for (int i = 0; i < unwrappedTypes.length; i++) {
 57			unwrappedTypes[i] = unwrapped[i].asTypeTag();
 58		}
 59		return unwrappedTypes;
 60	}
 61	
 62	public static NATTypeTag atValue(String typeName) {
 63		return atValue(AGSymbol.jAlloc(typeName));
 64	}
 65	
 66	public static NATTypeTag atValue(ATSymbol typeName) {
 67		return new NATTypeTag(typeName,
 68				             NATTable.atValue(new ATObject[] { OBJRootType._INSTANCE_ }));
 69	}
 70	
 71	public static NATTypeTag atValue(String typeName, NATTypeTag singleParent) {
 72		return new NATTypeTag(AGSymbol.jAlloc(typeName),
 73				             NATTable.atValue(new ATObject[] { singleParent }));
 74	}
 75	
 76	/**
 77	 * Types should not be created directly because it should be verified
 78	 * that their list of parent types is never empty. Types created
 79	 * with an empty parent list automatically get assigned the root type
 80	 * as their single parent.
 81	 */
 82	public static NATTypeTag atValue(ATSymbol typeName, ATTable parentTypes) {
 83		if (parentTypes == NATTable.EMPTY) {
 84			return new NATTypeTag(typeName, NATTable.atValue(new ATObject[] { OBJRootType._INSTANCE_ }));
 85		} else {
 86			return new NATTypeTag(typeName, parentTypes);
 87		}
 88	}
 89	
 90	/**
 91	 * The constructor is declared protected such that it cannot be used externally,
 92	 * but can be used by the OBJRootType class to create a type with an empty
 93	 * parent table, which is normally not allowed. Hence, by construction the only
 94	 * type with an empty parent table is the root type. 
 95	 */
 96	protected NATTypeTag(ATSymbol typeName, ATTable parentTypes) {
 97		typeName_ = typeName;
 98		parentTypes_ = parentTypes;
 99	}
100
101	public ATSymbol base_getTypeName() throws InterpreterException {
102		return typeName_;
103	}
104
105	public ATTable base_getSuperTypes() throws InterpreterException {
106		return parentTypes_;
107	}
108
109	/**
110	 * Native implementation of:
111	 * 
112	 *	def isSubtypeOf(supertype) {
113	 *		  (supertype.name() == name).or:
114	 *			  { (supertypes.find: { |type|
115	 *				  type.isSubtypeOf(supertype) }) != nil }
116	 *	};
117	 */
118	public ATBoolean base_isSubtypeOf(final ATTypeTag supertype) throws InterpreterException {
119		if (supertype.base_getTypeName().equals(typeName_)) {
120			return NATBoolean._TRUE_;
121		} else {
122			ATObject found = parentTypes_.base_find_(new NativeClosure(this) {
123				public ATObject base_apply(ATTable args) throws InterpreterException {
124					ATTypeTag type = get(args, 1).asTypeTag();
125					return type.base_isSubtypeOf(supertype);
126				}
127			});
128			return NATBoolean.atValue(found != NATNil._INSTANCE_);
129		}
130	}
131	
132	/**
133	 * Identity of types is based on their name
134	 */
135    public ATBoolean base__opeql__opeql_(ATObject comparand) throws InterpreterException {
136    	if (comparand.isTypeTag()) {
137    		return comparand.asTypeTag().base_getTypeName().base__opeql__opeql_(typeName_);
138    	} else {
139    		return NATBoolean._FALSE_;
140    	}
141    }
142	
143	public boolean isTypeTag() { return true; }
144	
145	public ATTypeTag asTypeTag() { return this; }
146	
147	public NATText meta_print() throws InterpreterException {
148		return NATText.atValue("<type tag:"+typeName_+">");
149	}
150	
151	/**
152	 * Types are singletons
153	 */
154	public ATObject meta_clone() throws InterpreterException {
155		return this;
156	}
157	
158    public ATTable meta_getTypeTags() throws InterpreterException {
159    	return NATTable.of(NativeTypeTags._TYPETAG_);
160    }
161	
162	/**
163	 * The root type of the type hierarchy: every type eventually
164	 * has this type as its parent.
165	 */
166	public static class OBJRootType extends NATTypeTag implements ATTypeTag {
167		
168		private final static AGSymbol _ROOT_NAME_ = AGSymbol.jAlloc("Type");
169		
170		public static final OBJRootType _INSTANCE_ = new OBJRootType();
171		
172		/**
173		 * The root type is named `Type and has no parent types
174		 */
175		private OBJRootType() {
176			super(_ROOT_NAME_, NATTable.EMPTY);
177		}
178
179		/**
180		 * The root type is only a subtype of the root type itself
181		 */
182		public ATBoolean base_isSubtypeOf(ATTypeTag supertype) throws InterpreterException {
183			return NATBoolean.atValue(supertype.base_getTypeName().equals(_ROOT_NAME_));
184		}
185		
186	}
187	
188}