[Haskell] compares :: Ord a => a -> a -> Ordering -> Ordering

[Ben Rudiak-Gould]

I just realized that the class Ord should have an additional method:

  class Eq a => Ord a where
    compares :: a -> a -> Ordering -> Ordering
    compares x y d = case compare x y of { EQ -> d ; o -> o }
    ...

This would make writing Ord instances much easier:

  instance (Ord a, Ord b, Ord c, Ord d) => Ord (a,b,c,d) where
    compares (a1,b1,c1,d1) (a2,b2,c2,d2) =
      compares a1 a2 . compares b1 b2 . compares c1 c2 . compares d1 d2

-- Ben

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