--- Simon Peyton-Jones <[EMAIL PROTECTED]> wrote:
> fixIO m = do { v <- newEmptyMVar
> ; result <- m (unsafePerformIO (takeMVar v))
> ; putMVar v result
> ; return result }
>
> Of course, this just begs the question of what
> exactly
> unsafePerformIO might mean, and we can only really
> answer that
> when we give an operational semantics to the
> functional part
> of the language as well as the imperative part.
Ok, I do see how fixIO works.. thanks!
I see what you mean about needing an operational
semantics for the functional part too.
Actually I was hoping to use fixIO to help explain
unsafeInterleaveIO, but I fixIO dont work that way:).
I can easily do unsafeInterleaveIO in terms of
unsafePerformIO, so perhaps that leaves me in the
quandry of needed operational semantics for the whole
language, so perhaps I better give up on that sticky
bit, for the moment.
This all started when I was trying to understand
what was going on in the SOE implementation of Fran.
They use getChannelContents (?) which just does more
magic that I could deal with. Maybe I will go back to
plan B: try to implement fran like system without lazy
event lists, since I cant think of anyway to construct
them without magic :)
Cheers!
__________________________________________________
Do You Yahoo!?
Get personalized email addresses from Yahoo! Mail - only $35
a year! http://personal.mail.yahoo.com/
_______________________________________________
Haskell mailing list
[EMAIL PROTECTED]
http://www.haskell.org/mailman/listinfo/haskell
