G'day all. On Wed, Jan 01, 2003 at 01:15:09PM +0100, Nicolas.Oury wrote:
From this, I think the safety become intuitive.
Maybe. Using the OI module from Richard Kieburtz' paper, I can write this: -- Bootstrap into the OI comonad main :: IO () main = return $! comain stdOI -- The following are the OI functions which we use. -- stdGetChar :: OI () -> Char -- stdPutStrLn :: OI String -> () comain :: OI a -> () comain w = coeval (w .>> show (a,b) =>> stdPutStrLn) where a = coeval (w .>> () =>> stdGetChar) b = coeval (w .>> () =>> stdGetChar) Even though a and b are identical, they return different values. I see two possibilities: Either my intuition is way off, or the OI comonad breaks referential transparency. It's possible that it's a fault in the implementation. It was clearly intended as an example only, after all. Cheers, Andrew Bromage