four.idr

module FourFunctor

data FourFunctor y = Four y y y y

traverseFourFunctor : Applicative f -> 
      (x -> f b) -> FourFunctor x -> f (FourFunctor b)
traverseFourFunctor constr f (Four w x y z) 
   = pure Four <$> (f w) <$> (f x) <$> (f y) <$> (f z)