> Haskell 98 libraries > > * Make each module export all the relevant types and functions that the > Prelude defines, so that a programmer who does not import the Prelude > can get access to all the (say) list types and functions by saying > import List. This involves extra exports from modules List, Monad, IO, > Maybe, Char. That's a jolly good idea! In the light of this change we possibly should also add a library module for Either (a type which is currently a bit neglected). > instance Functor (Either a) where > fmap f (Left a) = Left a > fmap f (Right a) = Right (f a) > instance Monad (Either String) where > Left a >>= k = Left a > Right a >>= k = k a > return = Right > mfail s = Left s Many of the functions contained in the library Maybe make sense for Either as well. Cheers, Ralf
