That could be done with a decorator, right? The decorator wraps a fuction in something non-callable and cocall is a function that unwraps it and calls it. On Mon, Aug 2, 2010 at 11:17 PM, Gregory Ewing <greg.ewing@canterbury.ac.nz> wrote:
On 03/08/10 04:39, Guido van Rossum wrote:
inevitably my coding went something like (1) forget to put a yield in, (2) frantically debug, (3) slap forehead, (4) add "if 0: yield" to the function, (5) continue with another instance of this, (6) lose sleep over the best place to spell the dummy yield and where to put it. At the same time I don't want to have to mark all my coroutines with a decorator, like Monocle requires (though maybe I should).
Would you be interested in a system which requires marking calls to coroutines, but tells you immediately when you have forgotten to mark such a call?
It might work something like this:
1. In a cofunction, a call to another cofunction must be marked with 'cocall', e,g.
z = cocall f(x, y)
2. Cofunctions *cannot* be called normally -- they do not have a __call__ method, only a __cocall__ method.
So if you try to call a cofunction without using cocall, you get an exception. If you try to call an ordinary function using cocall, you get an exception. If you try to use cocall but forget to declare the function with codef, you get an exception (because cocall would only be allowed inside a cofunction).
To start things off, a builtin function could be provided such as
def costart(f, *args, **kwds): return f.__cocall__(*args, **kwds)
which would return an object that a coroutine driver could treat as a generator.
I think this scheme would go a long way towards satisfying Antoine's desire to conceptually separate generators and coroutines. It would also enable an implementation to implement coroutines using a different mechanism from generators if it wanted to.
-- Greg
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