In the #haskell IRC channel, we just had a discussion on Data.Char predicates such as isAlpha, isUpper, isLower. The implementation of Data.Char is not Haskell 98 since Char specification in Haskell 98 only covers latin1. However, current predicates are confusing and intuitive properties does not hold. One example is this: [17:53:32] <newsham> > let cs = [minBound..maxBound]; us = filter isUpper cs; ls = filter isLower cs in take 5 $ (map toUpper ls) \\ us [17:53:33] <lambdabot> "\170\186\223I\312" isLower '\170' == True but you can't turn that into an uppercase letter. isUpper '170' == '\170'. I know that GHC team working on a rewrite of IO library for better Unicode support (I hope also includes better locale and charset support). Along the line to the new IO library work, it would also be good to have some cleanup in the Data.Char as well. Thanks, Ahn, Ki Yung