/interpreter/tags/at2dist110511/src/edu/vub/at/objects/ATNil.java

 1/**
 2 * AmbientTalk/2 Project
 3 * ATNil.java created on 26-jul-2006 at 12:05:01
 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.ATExpression;
32
33/**
34 * The methods understood by the native <tt>nil</tt> object.
35 * All other objects in the system delegate to <tt>nil</tt> eventually. Hence,
36 * <tt>nil</tt>'s methods may be invoked on all objects in the system.
37 * 
38 * @author tvcutsem
39 */
40public interface ATNil extends ATObject {
41
42	/**
43	 * The <tt>!=</tt> operator which returns <tt>false</tt> only if
44	 * the passed parameter equals <tt>nil</tt>.
45	 */
46	public ATBoolean base__opnot__opeql_(ATObject other) throws InterpreterException;
47	
48    /**
49     * The identity operator. In AmbientTalk, equality of objects
50     * is by default pointer-equality (i.e. objects are equal only
51     * if they are identical).
52     * 
53     * @return by default, true if the parameter object and this object are identical,
54     * false otherwise.
55     */
56    public ATBoolean base__opeql__opeql_(ATObject other) throws InterpreterException;
57    
58    /**
59     * This method is invoked when a new instance of the object is created
60     * using {@link this#base_new(ATObject[])}. The default implementation
61     * does nothing, but can be overridden to re-initialize the cloned
62     * instance.
63     */
64    public ATObject base_init(ATObject[] initargs) throws InterpreterException;
65    
66    /**
67     * Creates a new instance (a clone) of the receiver and initialises it
68     * by invoking its {@link this#base_init(ATObject[])} method.
69     */
70    public ATObject base_new(ATObject[] initargs) throws InterpreterException;
71}