lemming at henning-thielemann.de
Mon Jan 4 01:11:26 UTC 2016
On Mon, 4 Jan 2016, Oliver Charles wrote:
> Could you provide some examples where you have found it useful?
E.g. Set has Foldable instance, but not Functor. Using Mapped I can
implement argmax in a generic way, such that it also works on Set.
argmax :: (Ord b, Foldable f) => (a -> b) -> f a -> a
argmax f = snd . Fold.maximumBy (comparing fst) . Mapped (\a -> (f a, a))
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