On Thu, Nov 25, 2004 at 07:52:43PM +0100, Lennart Augustsson wrote: > As I'm sure you have gathered from all the answers you can't have the > latter and keep Haskell pure. But there is an interesting alternative > (at least theoretically). You could have a function like > > mkCatchJust :: IO ((Exception -> Maybe b) -> (c -> a) -> c -> (b -> a) -> a)
How is that different from this? mkReadFile :: IO (FilePath -> String) This is wrong. Even if I get a function as a result of an IO computation, I expect that function to be pure. > The cj function can be used in non-IO code and will behave just as you > want. But you have to create it in the IO monad, since it's behaviour > is not deterministic (especially not in the face of async exceptions). IO monad shouldn't be used to create non-deterministic functions. The whole point in using IO monad is that functions stay pure, regardless of their origin. Best regards, Tomasz _______________________________________________ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
