Re: Proposal: Add isLeft/isRight to Data.Either

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- I often use the 'when'-like combinator 'whenJust' in monadic code:

whenJust :: Monad m => Maybe a -> (a -> m ()) -> m () whenJust (Just x) a = a x whenJust _ _ = return ()

+1. whenJust is defined also in Agda.Utils.Monad, should also added to Control.Monad.

Off topic, but I have whenJust in my local library too, and I use it all the time.