[Python-ideas] Cofunctions - A New Protocol

[Jacob Holm]

On 2011-11-02 10:54, Greg Ewing wrote:
> Nick Coghlan wrote:
> 
>> However, as per the previous thread, I don't believe this needs to be
>> embedded in the bytecode by the compiler - it could instead be a
>> runtime switch in the eval loop, changing the way function calls and
>> iteration are handled.
> 
> Yes, but I'm no longer sure whether it's such a good idea
> to have no special syntax at all to mark a cofunction,
> seeing as cofunctionness won't be able to propagate through
> C calls, special methods, etc.
> 
> By having cofunctions declared in a distinctive way, you
> can look at the source and see exactly where the boundary is
> between cofunction and non-cofunction code. Without such
> markers, when you get an exception because you tried to
> suspend in a non-coroutine zone, it may not be obvious
> at which point along the call chain you made a mistake.
> 

If the switch Nick describes is available as a flag on the frame
objects, it would be easy to extend the traceback to show *exactly*
where you entered the no-coroutine zone that you are now failing to
suspend.  I don't think the additional syntax is helpful, and it would
be quite annoying to need to have two versions of every wrapper
function/decorator to make it useable in both contexts.

- Jacob