On Mar 2, 2010, at 10:33 PM, Levente Uzonyi wrote:
> On Tue, 2 Mar 2010, Henrik Sperre Johansen wrote:
>
>>
>>>> PS. For the not-so-faint-of-heart, open a Transcript and try evaluating:
>>>> |proc|
>>>> proc := [[Transcript show: 'Start!'. ] ensure: [Transcript show:
>>>> 'Finish!' Processor yield.]] newProcess.
>>>> proc resume.
>>>> Processor yield.
>>>> proc suspend.
>>>> proc terminate.
>>> Why don't we get it printing?
>> Forgot a . there, supposed to be
>>
>> |proc|
>> proc := [[Transcript show: 'Start!'. ] ensure: [Transcript show:
>> 'Finish!'. Processor yield.]] newProcess.
>> proc resume.
>> Processor yield.
>> proc suspend.
>> proc terminate.
>>
>> on my machine it prints:
>> *Start!Start!Finish!
>
> The problem occurs because Transcript >> #endEntry (sent from #show:)
> takes a while to execute, so the process (proc) prints 'Start!', but
> it gets terminated before execution reaches #resetContents (#reset in
> Squeak). So 'Start!' is still in the stream. Then our process executes the
> #ensure: block and it prints 'Start!' and 'Finish!' too.
Thanks for the explanation levente!
But I'm still dizzy :) why Transcript show: 'Finish' would also print 'start' ?
>
> There's worse problem with #ensure: and #terminate is that, a process
> executing an #ensure: block can be terminated. If you evaluate this code:
>
> | process stage1 stage2 stage3 counter |
> stage1 := stage2 := stage3 := false.
> counter := 0.
> process := [
> [ stage1 := true ] ensure: [
> stage2 := true.
> 1000000 timesRepeat: [ counter := counter + 1 ].
> stage3 := true ] ] newProcess.
> process resume.
> Processor yield.
> process suspend.
> process terminate.
> 1000 milliSeconds asDelay wait.
> { stage1. stage2. stage3. counter } explore
>
> you will find that stage1 and stage2 is reached as expected, but stage3 is
> not and counter is less than 1000000. That's because the forked process
> started evaluating the #ensure: block, but it was terminated by our process.
>
> Is this the expected behavior when sending #terminate to a process which is
> evaluating an #ensure: block?
>
>
> Cheers,
> Balázs & Levente
>
>
>>
>> *yay
>> Henry*
>> *
>
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