/interpreter/tags/at2dist130208/src/edu/vub/at/objects/ATClosure.java

  1/**
  2 * AmbientTalk/2 Project
  3 * ATClosure.java created on Jul 23, 2006 at 11:52:10 AM
  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.exceptions.XIllegalOperation;
 32
 33
 34/**
 35 * ATClosure is the public interface to a native AmbientTalk closure (a method + enclosing environment).
 36 * <p>
 37 * Since {@link ATMethod}s are always wrapped either at creation time (blocks) or during 
 38 * lookup (methods), ATClosures are by definition the only way methods and blocks 
 39 * can be encountered at the AmbientTalk base level. 
 40 * <p>
 41 * Closures should respond to the base_apply method, which should trigger the invocation of their encapsulating method in the
 42 * enclosed closure context.
 43 * <p>
 44 * Closures are sometimes also 'abused' to simply represent blocks of source code whose
 45 * body has to be evaluated not in the enclosed lexical context, but within the context
 46 * of another object. To facilitate such use, a closure provides the method 'base_applyInScope'
 47 * which will execute the enclosed method in the scope of the given object, rather than
 48 * in the enclosed lexical context.
 49 * 
 50 * @author smostinc
 51 * @author tvcutsem
 52 */
 53public interface ATClosure extends ATObject {
 54	
 55	/**
 56	 * Returns the encapsulated method. 
 57	 * 
 58	 * @return an {@link ATMethod} that returns the encapsulated method.
 59	 */
 60	public ATMethod base_method() throws InterpreterException;
 61
 62	/**
 63	 * Returns the scope of the closure.
 64	 * 
 65	 * @return an {@link ATMethod} that returns the scope of the closure.
 66	 */
 67	public ATContext base_context() throws InterpreterException;
 68	
 69	/**
 70	 * Applies the closure to the given arguments, already wrapped in a table.
 71	 * The enclosed method is executed in the context provided by the closure.
 72	 * 
 73	 * @param args the already evaluated arguments, wrapped in a table.
 74	 * @return the value of evaluating the method body in the context of the closure.
 75	 */
 76	public ATObject base_apply(ATTable args) throws InterpreterException;
 77	
 78	/**
 79	 * Applies the closure to the given arguments, already wrapped in a table.
 80	 * The enclosed method is executed in the context of the given object. The
 81	 * enclosed closure context is disregarded.
 82	 * <p>
 83	 * The context provided by an object is always equal to:
 84	 * <tt>ctx(cur=object,self=object,super=object.dynamicParent)</tt>
 85	 * 
 86	 * @param args the already evaluated arguments, wrapped in a table.
 87	 * @param scope the object that will act as self and as lexically enclosing scope.
 88	 * @return the value of evaluating the method body in the context of the given object scope.
 89	 */
 90	public ATObject base_applyInScope(ATTable args, ATObject scope) throws InterpreterException;
 91	
 92	/**
 93	 * Allows AmbientTalk programmers to write
 94	 * <code>{ booleanCondition }.whileTrue: { body }</code>
 95	 * which will execute body as long as the boolean condition evaluates to true.
 96	 * <p>
 97	 * More specifically, what the native implementation (expressed in AmbientTalk syntax) does is:
 98	 * <p>
 99	 * <code>
100	 * def whileTrue: body {
101	 *   self.apply().ifTrue: {
102	 *     body();
103	 *     self.whileTrue: body
104	 *   }
105	 * }
106	 * </code>
107	 * 	 
108	 * @param body the block of code that will be executed as long as the boolean condition evaluates to true.
109	 * @return the value of the last closure applied. 
110	 * @throws InterpreterException if raised inside the code closure.
111	 */
112	public ATObject base_whileTrue_(ATClosure body) throws InterpreterException;
113	
114	/**
115	 * Escape control construct <code>{ |quit| ... quit(val) ... }.escape()</code>
116	 * <p>
117	 * The escape control construct passes to its receiver block a function which
118	 * when invoked, immediately transfers control back to the caller of escape,
119	 * returning the value passed to quit.
120	 * <p>
121	 * If no value is passed to quit, nil is returned instead.
122	 * <p>
123	 * If quit is not invoked during the execution of the receiver block,
124	 * the block terminates normally, with its normal return value.
125	 * <p>  
126	 * If quit is invoked at the point where the call to escape has already returned,
127	 * either normally or via an exception or another escape call,
128	 * invoking quit will raise a {@link XIllegalOperation} exception.
129	 * 
130	 * @return the value passed to quit.
131	 */
132	public ATObject base_escape() throws InterpreterException;
133	
134}