DouKaku?

import Data.List (group,sort)

main :: IO ()
main = print $ qsort (-1) 10 [-1,9,4,8,9,6,3,9,5,2]

uniq :: Ord a => [a] -> [a]
uniq ns = map head $ group $ sort ns

qsort :: Integral a => a -> a -> [a] -> [a]
qsort _ _ [] = []
qsort _ _ ns | length (uniq ns) == 1 = ns
qsort min max ns = let mid = div (max + min) 2
                   in qsort min mid [y | y <- ns, y < mid] ++ qsort mid max [y | y <- ns, y >=mid ]