On Sat, Aug 7, 2010 at 3:05 AM, Carl M. Johnson <cmjohnson.mailinglist@gmail.com> wrote:
On Fri, Aug 6, 2010 at 9:12 PM, Greg Ewing wrote:
I've been doing some more hacking, and I now have a working implementation of cofunctions, which I'll upload somewhere soon.
I have also translated my yield-from examples to use cofunctions. In the course of doing this, the additional restrictions that cofunctions impose have already proved their worth -- I forgot a cocall, and it clearly told me so and pointed out exactly where it had to go!
This is good to hear. Without being too critical, I feel like saying that so far I've been following the cofunctions threads and waiting for compelling use cases. So, I'll be happy to see what you have there. It seems like the main use case that comes to mind for cofunctions is, essentially, quick and dirty cooperative multitasking. Of course, as we all know on the OS side of things, cooperative multitasking has been more or less phased out (I don't know about the embeded space. Probably it's hanging on there for real time purposes.) in favor of preemptive multitasking. But Python already has preemptive multitasking: it's called threads. Or, if one prefers, there is multiprocessing. Of course, those are relatively heavy-weight, but then again, so is adding new keywords and syntax. So, other use cases would be appreciated.
I am excited about the cofunctions PEP and features, since it will greatly improve the ability for monocle to have cooperative async tasks. An extension in the yield-from PEP allows us to return normal values without confusing semantics, cocall and codef allow us to avoid several types of errors, and in general the idea of a cofunction is promoted to a first-class tool, instead of an overloaded trick on top of generators. This need for these monocle chains is a much larger topic, but threads and processes introduce locking and state sharing complications which are much more involved than simply pausing a function until data is received. Not to mention the GIL. Cooperative multitasking in the OS was set aside, but async IO is alive and well. Allowing programmers to use async IO with a linear blocking look-alike syntax seems to be an important compromise which makes it easier to write efficient concurrent networking code. -Greg