Re: [Help-smalltalk] DynamicVariable in a Continuation

[Paolo Bonzini]

On 05/24/2011 08:20 AM, Derek Zhou wrote:
> Hi All,
> It looks like the sematic of DynamicVariable changed not very long ago; it
> was based on Notification, but it now just uses a ProcessVariable. Here is a
> simple testcase:
>
> DynamicVariable subclass: Seed [
>      ].
> Eval [
>      |b g1 g2|
>      b := [:v | v + Seed value].
>      g1 := Generator on: [ :g |
>          |v|
>          v := 0.
>          Seed use: 2 during: [
>              [ g yield: v.
>                v := b value: v ] repeat ]].
>      g2 := Generator on: [ :g |
>          |v|
>          v := 0.
>          Seed use: 3 during: [
>              [ g yield: v.
>                v := b value: v ] repeat ]].
>      Transcript nextPutAll: '%1 %2 %3 %4' % {
>          g1 next.
>          g2 next.
>          g1 next.
>          g2 next}; nl.
> ]
>
> It used to yield "0 0 2 3" but yields "0 0 3 3" now. I'd think "0 0 2 3" is
> the correct answer; the documantion specifically mentioned stackframes so
> the stackframes hopping from the Continuation should affect the variable,
> right?

You are correct.  The change was made because it was hundreds of time 
faster to use ProcessVariable, but I missed this use case.  I have to 
think about it.  Do you have any suggestion on how to name the classes 
to keep the current one available, and still provide "real" 
DynamicVariables?

Paolo