[Python-ideas] Cofunctions - Back to Basics

[Nick Coghlan]

On Sat, Oct 29, 2011 at 8:15 AM, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:
> Mark Shannon wrote:
>
>> Stackless provides coroutines. Greenlets are also coroutines (I think).
>>
>> Lua has them, and is implemented in ANSI C, so it can be done portably.
>
> These all have drawbacks. Greenlets are based on non-portable
> (and, I believe, slightly dangerous) C hackery, and I'm given
> to understand that Lua coroutines can't be suspended from
> within a C function.
>
> My proposal has limitations, but it has the advantage of
> being based on fully portable and well-understood techniques.


The limitation of Lua style coroutines is that they can't be suspended
from inside a function implemented in C. Without greenlets/Stackless
style assembly code, coroutines in Python would likely have the same
limitation.

PEP 3152 (and all generator based coroutines) have the limitation that
they can't suspend if there's a *Python* function on the stack. Can
you see why I know consider this approach categorically worse than one
that pursued the Lua approach?

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia