Isn't that a generator? A coroutine is where you have some number of functions A,B... and they can jump inside each other arbitrarily, like this:
A
|
|-jump!-B

    |
    |
    |

|-------+ #back to A
|
|

In ye olden days coroutines were used to make lightweight thread-style code, e.g. A is the user (gets input), and B is an AI player. They are still good for making lightweight threads withouot relying on external libraries or loljava.

Incidentally. python wins:
def func():

i=0
while i<10:
    yield i
    i+=1

(or, since we aren't passing any arguments, this works too:)
(i for in in range(10))
or, come to think of it, xrange(10) works too, but that doesn't explain anything.