Not OP but they meant https://hackage.haskell.org/package/base-4.16.1.0/docs/Data-Bifunctor.html#v:bimap https://hackage.haskell.org/package/base-4.16.1.0/docs/

Not OP but they meant https://hackage.haskell.org/package/base-4.16.1.0/docs/Data-Bifunctor.html#v:bimap https://hackage.haskell.org/package/base-4.16.1.0/docs/Data-... As you have the normal map function for Functors (using Haskell): > :t fmap fmap :: Functor f => (a -> b) -> f a -> f b you can have bimap for Bifunctors: > :t bimap bimap :: Bifunctor p => (a -> b) -> (c -> d) -> p a c -> p b d which specialised to pairs is: > :t bimap @(,) bimap @(,) :: (a -> b) -> (c -> d) -> (a, c) -> (b, d)