[Python-ideas] Cofunctions - Back to Basics

[Nick Coghlan]

On Thu, Oct 27, 2011 at 12:09 PM, Greg Ewing
<greg.ewing at canterbury.ac.nz> wrote:
> So, I've gone right back to my initial idea. The current version
> of the draft PEP can be found here:
>
> http://www.cosc.canterbury.ac.nz/greg.ewing/python/generators/cd_current/cofunction-pep-rev5.txt

----------
Certain objects that wrap other callable objects, notably bound methods,
will be given __cocall__ implementations that delegate to the underlying
object.
----------

That idea doesn't work when combined with the current idea in the PEP
for implicit cocall support inside cofunction definitions. Simple
method calls will see "Oh, this has __cocall__" and try to treat it
like a cofunction, when the underlying object is actually an ordinary
callable.

To make it work, you'll need some kind of explicit conversion API
(analogous to __iter__). Then, the expansion of calls in a cofunction
would look something like:

  _cofunc = obj.__cofunction__()
  if _cofunc is None:
    result = obj.__call__(*args, **kwds)
  else:
    result = yield from _cofunc(*args, **kwds)

However, you still potentially have some pretty serious ambiguity
problems - what happens inside an *actual* yield from clause? Or a for
loop iterator expression?

Cheers,
Nick.

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