Re: Why is there no Foldable instance for Either?

On 13-05-30 03:53 PM, Gabriel Gonzalez wrote:

I'm surprised that `Either` does not have a `Foldable` instance of the form:

import Data.Foldable import Data.Monoid

instance Foldable (Either e) where foldMap f (Left _) = mempty foldMap f (Right r) = f r

foldr _ z (Left _) = z foldr f z (Right r) = f r z

+1 for adding it