[Python-ideas] Cofunctions: It's alive! Its alive!

[Mike Meyer]

On Tue, 10 Aug 2010 08:10:44 -0400
Jack Diederich <jackdied at gmail.com> wrote:

> On Tue, Aug 10, 2010 at 3:22 AM, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:
> > Guido van Rossum wrote:
> >
> >> We'll see. I still cannot get my head around why cofunctions are so
> >> great.
> >
> [snip]
> > Here's the equivalent thing using cofunctions, complete with a
> > corresponding missing 'cocall':
> >
> [snip]
> > The exception and traceback resulting from this is crystal clear:
> >
> > Traceback (most recent call last):
> >  File "restaurant2.py", line 34, in <module>
> >    run()
> >  File
> > "/Local/Projects/D/Python/YieldFrom/3.1/Cofunctions-3.1.2/Examples/Simulation/simulation.py",
> > line 25, in run
> >    next(current_process)
> >  File "restaurant2.py", line 29, in customer
> >    hold(random.normalvariate(10, 5))
> > TypeError: Cofunction must be called with cocall or costart
> >
> > If this doesn't convince you of the utility of cofunctions or
> > something like them, I don't know what will.
> 
> So the benefit of cocalls is runtime type checking? Are your unit tests broken?

Isn't "runtime type checking" just another way to say "duck typing"?
Would you be happier if the error message was "'Cofunction' object is
not callable", so it was matched the error you get when you call other
non-callable objects?

Given two features that are otherwise equivalent - which seems to be
the case with yield-from vs cocalls - I'll take the one that makes
debugging easier.

> I was -0 on ABCs and function annotations because I was promised by
> people that liked them that I could safely ignore them.  I can't
> safely ignore this so I'm -1.

I don't see how you can ignore any feature that some program you're
trying to debug makes use of.

       <mike
-- 
Mike Meyer <mwm at mired.org>		http://www.mired.org/consulting.html
Independent Network/Unix/Perforce consultant, email for more information.

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