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/interpreter/tags/at2-build270707/src/edu/vub/at/objects/ATTypeTag.java

http://ambienttalk.googlecode.com/
Java | 85 lines | 8 code | 6 blank | 71 comment | 0 complexity | e84f3332b48eed10b91722ca97ee155e MD5 | raw file
 1/**
 2 * AmbientTalk/2 Project
 3 * ATTypeTag.java created on 18-feb-2007 at 15:55:09
 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;
29
30import edu.vub.at.exceptions.InterpreterException;
31import edu.vub.at.objects.grammar.ATSymbol;
32
33/**
34 * The public interface to a native type tag object.
35 * <p>
36 * Type tags consist of two properties:
37 * <ul>
38 * <li>they have a unique name by which they can be identified across the network.
39 *    In other words, the identity of a type is its name (= nominal typing).
40 * <li>they have a list of supertypes: a type is then a subtype of these supertypes.
41 * </ul>
42 * <p>
43 * Types have one important operation: one type can be tested to be a subtype of
44 * another type.
45 *  <p>
46 * Type tags are very similar to empty Java-like interface types, and their main purpose
47 * lies in the *classification* of objects. AmbientTalk Objects can be tagged with zero
48 * or more type tags.
49 *
50 * @author tvcutsem
51 */
52public interface ATTypeTag extends ATObject {
53
54	/**
55	 * Returns the name of this type tag.
56	 * 
57	 * @return an {@link ATSymbol} representing the unique name by which the type can be identified.
58	 */
59	public ATSymbol base_typeName() throws InterpreterException;
60	
61	/**
62	 * Returns a table with the supertypes of this type tag.
63	 * 
64	 * @return an {@link ATTable} with the super types of the receiver type tags.
65	 */
66	public ATTable base_superTypes() throws InterpreterException;
67	
68	/**
69	 * Returns true if this type tag is a subtype of a given type tag.
70	 * <p>
71	 * More specifically, what the native implementation (expressed in AmbientTalk syntax) does is:
72	 * <p>	 
73	 *	<code>
74	 *  def isSubtypeOf(supertype) {
75	 *		  (supertype.name() == name).or:
76	 *			  { (supertypes.find: { |stype| stype.isSubtypeOf(supertype) }) != nil }
77	 *	};
78	 *  </code>
79	 *  
80	 * @param other a type.
81	 * @return true if the receiver type is a subtype of the other type.
82	 */
83	public ATBoolean base_isSubtypeOf(ATTypeTag other) throws InterpreterException;
84	
85}