Remi Turk wrote:
On Sun, Oct 17, 2004 at 05:11:02PM +0100, Ben Rudiak-Gould wrote:
I don't think there's any problem with
type MVar = STMVar RealWorld
newMVar :: a -> ST s (STMVar s a) withMVar :: STMVar s a -> (a -> ST s b) -> ST s b ...
For that matter it seems like we could (should?) have
forkST :: ST s () -> ST s (STThreadId s) forkIO = forkST
But what semantics would they have? It cannot be the normal concurrency as AFAIK runST is supposed to be deterministic.
Okay, so I'm being silly. Forget forkST then. But STMVar is still okay, isn't it? The only MVars you could use in a state thread would be those you'd created in the same state thread, and without forkST they can't be accessed in a nondeterministic way. Their presence is pointless, true, but at least not unsafe. It does seem a bit of a hack, but it still seems preferable to the other alternatives currently on the table (namely unrestricted IO, a new SafeIO, or unsafeIOToST.newMVar). -- Ben