ghc-both

The Monoid instance for Maybe behaves like so:
> instance Monoid a => Monoid (Maybe a) where > mappend (Just x) (Just y) =
Just $ x <> y > mappend (Just x) Nothing = Just x > mappend Nothing (Just y) =
Just y > mappend Nothing Nothing = Nothing > > mempty = Nothing
Both is a newtype wrapper around Maybe providing this instance:
> instance Monoid a => Monoid (Both a) where > mappend (Just x) (Just y) = Just
$ x <> y > mappend _ _ = Nothing > > mempty = Just mempty.

          

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License: MIT
URL: https://hackage.haskell.org/package/both