Proposal: add Bounded instances for Maybe and Either

David Feuer david.feuer at
Tue May 8 03:19:12 UTC 2018

We can write

instance Bounded a => Bounded (Maybe a) where
  minBound = Nothing
  maxBound = Just maxBound

instance (Bounded a, Bounded b) => Bounded (Either a b) where
  minBound = Left minBound
  maxBound = Right maxBound

While Bounded intentionally does not have an Ord superclass, I think it's
worth mentioning that these are the instances that arise naturally from the
Ord instances for the types in question.
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