Re: Add instance Alternative (Either e)

On Tue, Aug 6, 2019 at 9:40 PM Dannyu NDos wrote:

instance Monoid e => Alternative (Either e) where empty = left mempty Left x <|> Left y = Left (x <> y) Left _ <|> y = y x <|> _ = x

Leftmost Right is returned for sake of consistence with Semigroup instance.

Related: https://ghc.haskell.org/trac/ghc/ticket/9588