On Wed, Jan 1, 2014 at 2:55 PM, gettimothy gettimothy@zoho.com wrote:
In Eliot's first example on fixing the reentrancy problemhttp://www.mirandabanda.org/cogblog/category/cog/page/14/that uses "factorial copy" for the recursion.
I modifed his code:
| factorial | factorial := [:n| n = 1 ifTrue: [1] ifFalse: [(factorial copy value: n - 1) * n]]. (1 to: 10) collect: factorial copy
into something I could trace out a bit easier.
| factorial fc | Transcript clear. factorial := [:n | n = 1 ifTrue:[ Transcript show: ' n=', (n asString),' ', (thisContext class name), '(', (thisContext identityHash asString),')' . Transcript show: '--sender-->', (thisContext sender) class name, '(', (thisContext sender) identityHash asString,')'. Transcript show: '--home-->', (thisContext home) class name, '(', (thisContext home) identityHash asString,')'; cr.
Transcript show: '++++++++++++++++++++++++++++++++++++++++';cr. "thisContext explore. " 1 ] ifFalse:[ Transcript show:'-----------------------------------------------';cr. Transcript show: ' n=', (n asString),' ', (thisContext class name), '(', (thisContext identityHash asString),')' . Transcript show: '--sender-->', (thisContext sender) class name, '(', (thisContext sender) identityHash asString,')'. Transcript show: '--home-->', (thisContext home) class name, '(', (thisContext home) identityHash asString,')'; cr.
(factorial copy value: n-1) * n ]].Transcript show:' factorial = ' , (factorial class name),'(',factorial identityHash asString,')'. Transcript show: '--sender-->', (factorial sender) class name, '(', (factorial sender) identityHash asString,')'. Transcript show: '--home-->', (factorial home) class name, '(', (factorial home) identityHash asString,')'; cr. Transcript show: '^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^';cr.
fc := factorial copy .
Transcript show:' fc = ' , (fc class name),'(',fc identityHash asString,')'. Transcript show: '--sender-->', (fc sender) class name, '(', (fc sender) identityHash asString,')'. Transcript show: '--home-->', (fc home) class name, '(', (fc home) identityHash asString,')'; cr. Transcript show: '^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^';cr.
thisContext inspect. factorial inspect. fc inspect. (1 to: 3) collect: fc
The Transcript output is as follows:
factorial = BlockContext(694)--sender-->UndefinedObject(3840)--home-->MethodContext(2677) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ fc = BlockContext(3934)--sender-->UndefinedObject(3840)--home-->MethodContext(2677) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ n=1 BlockContext(3934)--sender-->MethodContext(2367)--home-->MethodContext(2677)
++++++++++++++++++++++++++++++++++++++++
n=2 BlockContext(3934)--sender-->MethodContext(2367)--home-->MethodContext(2677) n=1 BlockContext(1198)--sender-->BlockContext(3934)--home-->MethodContext(2677)
++++++++++++++++++++++++++++++++++++++++
n=3 BlockContext(3934)--sender-->MethodContext(2367)--home-->MethodContext(2677)
n=2 BlockContext(1684)--sender-->BlockContext(3934)--home-->MethodContext(2677) n=1 BlockContext(2780)--sender-->BlockContext(1684)--home-->MethodContext(2677) ++++++++++++++++++++++++++++++++++++++++
http://www.mirandabanda.org/cogblog/category/cog/page/14/ Look at the 3'rd line, where n=1. Why is the sender-->MethodContext(2367) instead of sender-->MethodContext(2677) What created that new MethodContext?
That would be the activation of Interval>>collect:, which performs the first call of the copied factorial block for each 1 through 3.
collect: aBlock | nextValue result | result := self species new: self size. nextValue := start. 1 to: result size do: [:i | result at: i put: (*aBlock value: nextValue*). nextValue := nextValue + step]. ^ result