/interpreter/tags/at2dist110511/src/edu/vub/at/objects/grammar/ATDefExternalMethod.java

 1/**
 2 * AmbientTalk/2 Project
 3 * ATDefExternalMethod.java created on 15-nov-2006 at 19:23:51
 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.grammar;
29
30import edu.vub.at.objects.ATTable;
31import edu.vub.at.objects.natives.NATClosureMethod;
32
33/**
34 * The public interface to an external method definition AG element.
35 * 
36 * <p>
37 * Example: <code>def o.m() { body }</code>
38 * </p><p>
39 * There are three ways to evaluate such expressions with respect to what context should be
40 * active when the method is invoked upon the object:
41 * <ol>
42 *  <li> The newly defined method is wrapped in a closure thereby fixing the lexical scope that was
43 *     active at method definition/addition time, as well as the values of 'self' and 'super'.
44 *     This has the advantage that within the externally added method body:
45 *      a) the adding object can still access its lexical scope.
46 *      b) the adding object can *not* access the scope of the object it is adding a method to.
47 *     This has the disadvantage that within the externally added method body,
48 *     'self' and 'super' keep on referring to the lexically active self and super. This has the
49 *     disadvantage that the newly added method cannot perform 'super sends', nor is the value of
50 *     'self' correct when the method is invoked through a child of o.</li>
51 *  <li> The newly defined method is added as-is to the object. This has roughly the reverse
52 *     effects of option 1: the adding object loses its lexical scope (error-prone and dangerous!)
53 *     but the values for self and super are correct. It is as if the method was really defined
54 *     in the scope of the original object.</li>
55 *  <li> The newly defined method is wrapped in a special 'objectless' closure that captures the
56 *     lexical scope of the adding object but *not* the values of 'self' and 'super'. When the
57 *     added method is subsequently invoked, its lexical scope will still be that of the adding
58 *     object (hence, having the benefits of option 1) while the values of 'self' and 'super'
59 *     will be correct with respect to the method invocation on o (or a child of o) (hence,
60 *     having the benefits of option 2.</li>
61 * </ol>
62 * </p><p>
63 * AmbientTalk implements the third option, by means of a {@link NATClosureMethod}.
64 * </p>
65 * 
66 * @author tvc
67 */
68public interface ATDefExternalMethod extends ATDefinition {
69
70	/**
71	 * Example: <code>`{ def o.m() { 5 } }.statements[1].receiver == `o</code>
72	 * @return the receiver on which the method will be defined
73	 */
74	public ATSymbol base_receiver();
75	
76	/**
77	 * Example: <code>`{ def o.m() { 5 } }.statements[1].selector == `m</code>
78	 * @return the selector of the new method
79	 */
80	public ATSymbol base_selector();
81	
82	/**
83	 * Example: <code>`{ def o.m(a, @b) { b } }.statements[1].arguments == `[a, @b]</code>
84	 * @return the argument list of the new method
85	 */
86	public ATTable base_arguments();
87	
88	/**
89	 * Example: <code>`{ def o.m() { o.n(); 1+2+3 } }.statements[1].bodyExpression == `{o.n(); 1.+(2).+(3)}</code>
90	 * @return the body of the new method
91	 */
92	public ATBegin base_bodyExpression();
93	
94	/**
95	 * Example: <code>`{ def o.m() @[Getter] { 5 } }.statements[1].annotations == `[Getter]</code>
96	 * @return the annotations of the new method
97	 */
98	public ATExpression base_annotationExpression();
99}