Issue resolved.

Ok. I just updated the description. This should clarify enough the semantics of the coroutine interface:

type Coroutine r = ContT r IO ()
type Queue r = IORef [Coroutine r]

Here, you have to implement coroutines as separate threads, using an IORef to hold a list of continuations "waiting to run".

Interface:

yield :: Queue r -> Coroutine r
fork :: Queue r -> Coroutine r -> Coroutine r

• yield q: yields the processor to next thread in q.
  • Hint: enqueue the current continuation and run the next thread in q.
• fork q p: starts a new thread in q running p.
  • Hint: enqueue the current continuation, run p, and run the next thread in q.

Fixed. Solutions based on Yall module are now rejected.

No, it is not intended to use that library. I'll look at it, thanks.

The author updated the tests.