unsafeInterleaveIO

[Simon Marlow]

=20
> That's exactly what's there now, and it doesn't produce interleaving.
> Hugs doesn't have a global thread pool -- each instance of=20
> unsafePerformIO
> has its own.  Once the side computation starts, it runs to completion
> before returning to the main thread.  Even if it yields, only threads
> spawned inside the unsafePerformIO can take over.  A global=20
> thread pool
> doesn't seem feasible with the current implementation of concurrency
> in Hugs.  Concurrency is implemented in the libraries; a=20
> blocked thread
> is a continuation, and it's not clear how to construct that=20
> continuation in a pure context.

I'm sure you're right, but I don't understand why an unsafePerformIO has
to have its own thread at all.  It's fine for an unsafePerformIO to run
to completion before anything else happens - in fact that's exactly what
I'd expect in a single-threaded system.

Cheers,
	Simon