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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
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