[pypy-dev] Stacklets

[Antonio Cuni]

Hi Armin,

On 11/08/11 18:46, Armin Rigo wrote:

> Moreover, we can give it an interface very similar to generators.  A
> genlet object has a primitive method send(x), a wrapper next() that
> just calls send(None), and is an iterator.  Example:
>
> @genlet
> def f(gen, a, b):
>      for i in range(a, b):
>          gen.send(i)
>
> for x in f(10, 20):
>      print x
>

I'm not sure to fully understand how it would work. Let's rewrite it this way:

def f_inner(gen, a, b):
     ...
f = genlen(f_inner)
...

When I call f(10, 20), it returns a genlet object, which is an iterator with a 
next() method.

When the for loop calls gen.next(), the execution of f_inner is resumed until 
it calls gen.send(i), and then "i" is used as a return value for next(). Is it 
correct so far?

What I don't get is how all these calls interact with the C stack.  I suppose 
that when I call "gen.send(i)" the C stack for f_inner is saved inside and 
moved away (and "gen" has a reference to it), and then it resumed later when I 
call gen.next().

But, what happens to the C stack of the code which executes "for x in f(10, 
20)"?  Is it saved as soon as I switch to the genlet?  Are the caller/callee 
genlets symmetrical? Is there a concept of "main genlet" or something like that?

thanks,
Anto