On 6 May 2014 19:40, Tobias Pape <Das.Linux at gmx.de> wrote:
> Woulnd't it be better to make that a
> dynamic variable? Because it is used as such?
> I think this would save some stackwalking.
>
> (why do I think so? I looks too similar to Seaside’s
> use of Dynamic variables)

It is indeed a dynamic variable. It's a _delimited_ dynamic variable,
if you want to get super picky. Last time I checked Seaside used an
on:do: to cut the WaPartialContinuation out of the stack. (I'm running
on memory that's possibly 5 years old. Things might have changed.)

Either way, this is exactly the right kind of dynamic variable. The
DynamicVariable/process-local variable is the wrong kind of dynamic
variable, the undelimited kind. It catches the _entire_ dynamic scope
of a variable and thus is incompatible with continuations and stack
slicing. Which we happen to do a lot, in Smalltalk.

Now there is definitely scope to talk about whether we can improve the
stack-walking. It's what Henry Baker would call "deep binding" [1],
and if I understand correctly, we'd need to make some seriously deep
interventions to implement shallow binding (which has a much lower
read cost).

frank

[1] http://home.pipeline.com/~hbaker1/ShallowBinding.html

> Best
>         -Tobias
>
> On 06.05.2014, at 17:54, commits at source.squeak.org wrote:
>
>> Chris Muller uploaded a new version of Environments to project Squeak 4.5:
>> http://source.squeak.org/squeak45/Environments-cwp.47.mcz
>>
>> ==================== Summary ====================
>>
>> Name: Environments-cwp.47
>> Author: cwp
>> Time: 22 March 2014, 7:53:17.666 pm
>> UUID: 12e68b45-ec35-4eff-985b-8008d6f03339
>> Ancestors: Environments-ul.46
>>
>> Rename EnvironmentRequest to CurrentEnvironment and use it to implement Environment class>>current.
>>
>> =============== Diff against Environments-ul.46 ===============
>>
>> Item was added:
>> + Notification subclass: #CurrentEnvironment
>> +     instanceVariableNames: ''
>> +     classVariableNames: ''
>> +     poolDictionaries: ''
>> +     category: 'Environments-Loading'!
>>
>> Item was added:
>> + ----- Method: Environment class>>current (in category 'accessing') -----
>> + current
>> +     ^ CurrentEnvironment signal ifNil: [self default]!
>>
>> Item was changed:
>>  ----- Method: EnvironmentLoader>>evaluate: (in category 'as yet unclassified') -----
>>  evaluate: chunk
>>       ^ [Compiler evaluate: chunk environment: environment]
>> +             on: CurrentEnvironment
>> -             on: EnvironmentRequest
>>               do: [:req | req resume: environment]!
>>
>> Item was changed:
>>  ----- Method: EnvironmentLoader>>evaluate:logged: (in category 'as yet unclassified') -----
>>  evaluate: chunk logged: aBoolean
>>       ^ [Compiler evaluate: chunk environment: environment logged: aBoolean]
>> +             on: CurrentEnvironment
>> -             on: EnvironmentRequest
>>               do: [:req | req resume: environment]!
>>
>> Item was removed:
>> - Notification subclass: #EnvironmentRequest
>> -     instanceVariableNames: ''
>> -     classVariableNames: ''
>> -     poolDictionaries: ''
>> -     category: 'Environments-Loading'!
>>
>>
>
>
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>