Mario

Do you think there is any alternative to this Rank2.Functor instance? instance (Rank1.Functor g, Rank2.Functor h) => Rank2.Functor (Compose g h) where f ~(Compose a) = Compose ((f ) Rank1....

Can you think of any application of the `Lexicographic` class other than a radix tree? If not, the best place for the class would probably be within the radix tree...

You make some good points. Yes, I mistakenly swapped the ``(a `isPrefixOf` b)