module Constant where

newtype Constant a b =
    Constant { getConstant :: a }
    deriving (Eq, Ord, Show)

instance Functor (Constant a) where
    fmap _ (Constant x) = Constant x

instance Monoid a
  => Applicative (Constant a) where
      pure x = Constant mempty
      (Constant x) <*> (Constant y) = Constant $ mappend x y