[Pkg] The Trunk: Kernel-eem.474.mcz

[commits at source.squeak.org]

Eliot Miranda uploaded a new version of Kernel to project The Trunk:
http://source.squeak.org/trunk/Kernel-eem.474.mcz

==================== Summary ====================

Name: Kernel-eem.474
Author: eem
Time: 22 July 2010, 1:42:05.4 pm
UUID: 292f2cc5-ba81-4d03-a64f-4e7cb878d68f
Ancestors: Kernel-eem.473

BlockClosure>>#once Travis Griggs' neat idiom for interning values of computations.  Use e.g. as in
	myResourceMethod
		^[time-consuming computation] once

=============== Diff against Kernel-eem.473 ===============

Item was added:
+ ----- Method: CachedBlockClosure>>value (in category 'evaluating') -----
+ value
+ 	^cachedValue!

Item was added:
+ ----- Method: BlockClosure>>becomeUncached (in category 'private') -----
+ becomeUncached
+ 	"The receiver is already uncached."
+ 	^self!

Item was added:
+ ----- Method: CachedBlockClosure>>becomeCached (in category 'private') -----
+ becomeCached
+ 	"The receiver is already cached."
+ 	^self!

Item was added:
+ ----- Method: BlockClosure>>becomeCached (in category 'private') -----
+ becomeCached
+ 	self become: ((CachedBlockClosure new: self size)
+ 						outerContext: outerContext
+ 						startpc: startpc
+ 						numArgs: numArgs
+ 						cachedValue: self value
+ 						copiedValues: self)!

Item was added:
+ BlockClosure variableSubclass: #CachedBlockClosure
+ 	instanceVariableNames: 'cachedValue'
+ 	classVariableNames: ''
+ 	poolDictionaries: ''
+ 	category: 'Kernel-Methods'!
+ 
+ !CachedBlockClosure commentStamp: 'eem 7/22/2010 12:34' prior: 0!
+ I'm a BlockClosure with an added instance variable for storing the once upon a time result of evaluating myself when I was simple BlockClosure. This is triggered by sending #once to a normal BlockClosure. Future sends of once will simply return this value rather than evaluate myself. When sent value, I revert back to a BlockClosure.  Originally by Travis Griggs, from whom we copy this idea with thanks.
+ 
+ Instance Variables
+ 	cachedValue	<Object>
+ 
+ cachedValue
+ 	- result of having sent value to myself when i was just a BlockClosure!

Item was added:
+ ----- Method: CachedBlockClosure>>once (in category 'evaluating') -----
+ once
+ 	^cachedValue!

Item was added:
+ ----- Method: CachedBlockClosure>>outerContext:startpc:numArgs:cachedValue:copiedValues: (in category 'initialize-release') -----
+ outerContext: aContext startpc: aStartpc numArgs: argCount cachedValue: aValue copiedValues: anArrayOrNil
+ 	cachedValue := aValue.
+ 	super outerContext: aContext startpc: aStartpc numArgs: argCount copiedValues: anArrayOrNil!

Item was added:
+ ----- Method: CachedBlockClosure>>becomeUncached (in category 'private') -----
+ becomeUncached
+ 	self become: (BlockClosure 
+ 					outerContext: outerContext
+ 					startpc: startpc
+ 					numArgs: numArgs
+ 					copiedValues: self)!

Item was added:
+ ----- Method: BlockClosure>>once (in category 'evaluating') -----
+ once
+ 	"Answer and remember my value, answering exactly the same object in any further sends
+ 	 of once or value until I become uncached.  This allows one to intern values with the idiom
+ 		myResourceMethod
+ 			^[expression] once.
+ 	 The expression will be evaluated once and its result returned for any subsequent evaluations.
+ 	 Originally by Travis Griggs, from whom we copy this idea with thanks."
+ 	numArgs ~= 0 ifTrue:
+ 		[self error: 'once should only be used with niladic blocks'].
+ 	self becomeCached.
+ 	^self once!