At 2002-01-18 03:06, Cagdas Ozgenc wrote:

Same story, you shouldn't have had a Container of Char only in the first place.

Well, what about a file-handle? Not necessarily exactly a Container (though it might be), but it's always "of Char", or better yet, "of Word8". You could make a generalised file-handle to be of anything, but your read and write functions would necessarily have to be restricted. For instance, given this: class Stream1 c where read :: c a -> Integer -> IO [a] write :: c a -> [a] -> IO () data FileHandle1 a = ... fileRead :: FileHandle1 Word8 -> Integer -> IO [Word8] fileWrite :: FileHandle1 Word8 -> [Word8] -> IO () ...you cannot make FileHandle1 an instance of Stream1. However, you could do this: class Stream2 s a | s -> a where read :: s -> Integer -> IO [a] write :: s -> [a] -> IO () data FileHandle2 = ... fileRead :: FileHandle2 -> Integer -> IO [Word8] fileWrite :: FileHandle2 -> [Word8] -> IO () instance Stream2 FileHandle2 Word8 where read = fileRead write = fileWrite -- Ashley Yakeley, Seattle WA