On 25/03/2015 at 15:06:47 -0500, M Farkas-Dyck wrote: > https://hackage.haskell.org/package/witherable > > Interesting name choice... This has superclass Traversable tho, which is not needed as wither f xs = catMaybes <$> traverse f xs filterA f = mapMaybeA (\ x -> (x <$) . guard <$> f x)