[Haskell-cafe] mapFst and mapSnd

[Alexander Solla]

On Thu, May 30, 2013 at 10:56 PM, Tony Morris <tmorris at tmorris.net> wrote:

> class BinaryFunctor f where
>   bimap :: (a -> c) -> (b -> d) -> f a b -> f c d
>
> mapFst = (`bimap id`)
> mapSnd = bimap id
>

There's a bifunctors package with:

class Bifunctor f where
    bimap :: ...
    first :: a -> b -> f a c -> f b c
    second :: b -> c -> f a b -> f a c
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