[Python-Dev] Stackless Python

[Phillip J. Eby]

At 08:17 PM 5/31/04 -0700, Guido van Rossum wrote:
> > If soft-switching is portable (i.e. pure C, no assembly), and is
> > exposed as a library module (so that Jython et al can avoid
> > supporting it), then perhaps a PEP for adding that functionality to
> > mainstream Python would be meaningful.
>
>Anything that can be supported by a pure extension module is fair game
>IMO.  But it was my understanding that Stackless requires changes to
>the VM.

I did mean *exposed* as a library module, not implemented as one.  I am 
aware of the VM change.


>   And I definitely don't want people to get into a habit of
>writing code that relies on deep recursion that is only supported by
>Stackless, only to find that it doesn't work in Jython etc.

 From the docs of sys.setrecursionlimit():

"""The highest possible limit is platform-dependent. A user may need to set 
the limit higher when she has a program that requires deep recursion and a 
platform that supports a higher limit. This should be done with care, 
because a too-high limit can lead to a crash."""

Seems to me that the platform-specific nature of this is already established.


> > If that gets in, then the other 5% can always sneak in later via
> > feature creep.  ;) Or, more importantly (if I understand correctly),
> > it could be separately distributed as an add-on for platforms that
> > can support it.
>
>Hey, that's what Stackless already does.  Why is that approach
>suddenly not good enough any more?

I didn't say that.  I was just suggesting that if people had specific 
features of Stackless that they wanted to see in CPython, that it would be 
best for them to write a PEP specifically addressing the desired 
feature(s), rather than asking "why isn't CPython stackless?"