RE: [Haskell] IO Regions in Haskell98

| however that there is a Haskell98 implementation of IO regions. The | solution involves no higher-ranked types, and works both in GHC and | Hugs. The idea is trivial: given | | > newtype Q = Q Handle | > newtype IOM a = IOM (IO a) | > qGetChar :: Q -> IOM Char | > withFile :: FilePath -> (Q -> IOM a) -> IOM a | | we wish to assure that the handle Q never escapes, neither explicitly | nor implicitly. Don't side effects kill you? withFile "foo" (\q -> writeIORef var q) So would unsafePerformIO withFile "foo" (\q -> return (unsafePerformIO (qGetChar q))) Simon