----- Original Message ----- 
From: "Ralph Johnson" <johnson at cs.uiuc.edu>
To: "The general-purpose Squeak developers list" 
<squeak-dev at lists.squeakfoundation.org>
Sent: Wednesday, November 07, 2007 9:55 PM
Subject: Re: What would Squeak be like without non-local returns


> On 11/7/07, Andreas Raab <andreas.raab at gmx.de> wrote:
>> Ralph Johnson wrote:
>> > Consider the code
>> >
>> > object eventual: [...  ^3]
>> > ...
>> > ^4
>> >
>> > Depending on the missing code, it could return either 3 or 4.  If not,
>> > something is very strange, and the language is no longer Smalltalk.
>>
>> Not at all. Eventual/future sends introduce a new unit of concurrency
>> and the only thing we're arguing is whether that second unit of
>> concurrency will be executed before the first one. In E/Croquet this is
>> not possible, but it is really no different from, e.g.,
>>
>> Object>>foo
>>    [^3] forkAt: Processor activePriority-1.
>>    ^4
>>
>> When you run this, it will return 4 (every time) and fall over the
>> non-local return later (every time).
>
> But that wasn't what I said.  Your code is different from mine.  Note the 
> ...
>
> For example,
>
> Object >>foo
>  [^3] fork.
>  self halt.
>  ^ 4
>
> returns 3.

No, this halts, on the calling Process, and signals a BlockCannotReturn 
Error, on the forked Process, presumably because the returnContext is nil. 
Without the halt and with any number of statements (...), it would return 3.

Rob