instance consArray :: Cons (Array a) (Array b) a b where
  _Cons = L.prism (uncurry (:)) $ \arr -> case A.uncons arr of
    Nothing -> Left []
    Just r -> Right (Tuple r.head r.tail)

class Cons s a | s -> a where
  _Cons :: LE.Setter a (s -> s) a s

instance consList :: Cons (L.List a) a where
  _Cons f a l = f a <> l

prism :: forall s t a b. (b -> t) -> (s -> Either t a) -> Prism s t a b
prism to fro pab = dimap fro (either identity identity) (right (rmap to pab))