proposal #4095: add Applicative instance for Either

[Edward Kmett]

+1

On Tue, May 25, 2010 at 8:41 AM, Ross Paterson <ross at soi.city.ac.uk> wrote:

> The proposal is to add this instance to Control.Applicative:
>
>    instance Applicative (Either e) where
>        pure          = Right
>        Left  e <*> _ = Left e
>        Right f <*> r = fmap f r
>
> This is not the only possible instance for Either, but this one is
> compatible with the usual Monad instance.
>
> Deadline: 15th June 2010
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