[Python-Dev] 'stackless' python?

[Christian Tismer]

Tim Peters wrote:
> 
> [Christian Tismer]
> > ...
> > Yup. With a little counting, it was easy to survive:
> >
> > def main():
> >     global a
> >     a=2
> >     thing (5)
> >     a=a-1
> >     if a:
> >         saved.throw (0)
> 
> Did "a" really need to be global here?  I hope you see the same behavior
> without the "global a"; e.g., this Scheme:

(Hüstel) Actually, I inserted the "global" later. It worked as well
with a local variable, but I didn't understand it. Still don't :-)

> Or does brute-force frame-copying cause the continuation to set "a" back to
> 2 each time?

No, it doesn't. Behavior is exactly the same with or without
global. I'm not sure wether this is a bug or a feature.
I *think* 'a' as a local has a slot in the frame, so it's
actually a different 'a' living in both copies. But this
would not have worked.
Can it be that before a function call, the interpreter
turns its locals into a dict, using fast_to_locals?
That would explain it.
This is not what I think it should be! Locals need to be
copied.

> > and needs a much better interface.
> 
> Ya, like screw 'em and use threads <wink>.

Never liked threads. These fibers are so neat since
they don't need threads, no locking, and they are
available on systems without threads.

> > But finally I'm quite happy that it worked so smoothly
> > after just a couple of hours (well, about six :)
> 
> Yup!  Playing with Python internals is a treat.
> 
> to-be-continued-ly y'rs  - tim

throw(42) - chris

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