binary.hs

-- Trick for expressing contexts like (∀ a. Binary a => Binary (f a))
--
-- This type class says that if we have dictionary for data type `a' we can 
-- construct dictionary for `f a' or equivalently that if `a' is instance of 
-- Binary `f a' is instance too.
class Binary2 f where
  binaryDict :: BinaryDict a -> BinaryDict (f a)

data BinaryDict a where
  BinaryDict :: Binary a => BinaryDict a