Folks I'm back to tidying up the Haskell Report. In the Numeric library, there is the useful function readFloat :: RealFloat a => ReadS a But you can't use it for reading rationals, because Rational isn't in RealFloat! This is a Royal Pain, and entirely unnecessary. In fact, readFloat uses only operations from the RealFrac class, so it could equally well have type readFloat :: RealFrac a => ReadS a I'm strongly inclined to make this change. It breaks no programs, and it fixes a real bug i.e. there is no way to read a "103" as a Rational. Simon