Haskell implementation of the quicksort algorithm

Haskell Quicksort

quicksort :: (Ord a) => [a] -> [a]
quicksort [] = []
quicksort (x:xs) = let lesser = filter (< x) xs
                       greaterThanOrEqual = filter (>= x) xs
                   in quicksort lesser ++ [x] ++ quicksort greaterThanOrEqual