:: Ord a => [a] -> [a] -package:Cabal package:data-ordlist is:exact

On ordered lists, nub is equivalent to nub, except that it runs in linear time instead of quadratic. On unordered lists it also removes elements that are smaller than any preceding element.
nub [1,1,1,2,2] == [1,2]
nub [2,0,1,3,3] == [2,3]
nub = nubBy (<)
The sort function implements a stable sorting algorithm. It is a special case of sortBy, which allows the programmer to supply their own comparison function.
The nubSort function is equivalent to nub . sort, except that duplicates are removed as it sorts. It is essentially the same implementation as Data.List.sort, with merge replaced by union. Thus the performance of nubSort should better than or nearly equal to sort alone. It is faster than both sort and nub . sort when the input contains significant quantities of duplicated elements.