Proposal: Add `maxOn` and `minOn` functions to Data.Ord

[Jon Fairbairn]

Daniel Díaz Casanueva <dhelta.diaz at gmail.com> writes:

> I think these are useful in general, and that they would make a good
> addition to `Data.Ord`. The names are inspired by `sortOn`. Definitions:
>
> ```
> minOn :: Ord b => (a -> b) -> a -> a -> a
> minOn f x y =
>   case comparing f x y of
>     LT -> x
>     _ -> y

Bad name; it’s too close to on min, which has the same type.

-- 
Jón Fairbairn                                 Jon.Fairbairn at cl.cam.ac.uk