in-place quick sort

gistfile1.hs

import Data.Vector.Generic
import qualified Data.Vector.Generic.Mutable as M 

iqsort :: (Vector v a, Ord a) => v a -> v a
iqsort = modify go where
         go xs  | len < 2   = return ()
                | otherwise = do
                    p <- xs `M.read` (len `div` 2)
                    m <- M.unstablePartition (< p) xs
                    go $ M.slice 0     m         xs
                    go $ M.slice (m+1) (len-m-1) xs
                where len = M.length xs