On Mon, Aug 11, 2003 at 12:15:57PM +0100, Simon Marlow wrote:

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I'm sure you're right, but I don't understand why an unsafePerformIO has to have its own thread at all.

In Hugs, threads exist only in the IO monad.

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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.

Sure, but is that what you'd expect of unsafeInterleaveIO?

Certainly! Consider the common use of unsafeInterleaveIO to return the contents of a file lazilly. You would write something like this: getContents = unsafeInterleaveIO f where f = do c <- getChar xs <- unsafeInterleaveIO f return (c:xs) as you can see, it's fine for each invocation of f to run to completion, because it uses nested unsafeInterleaveIO to get the interleaving. Cheers, Simon