quicksort implementation in haskell

qsort.hs

import Data.List

assert :: Bool -> ()
assert False = error "assertion failed"
assert True = ()

qSort :: Ord a => [a] -> [a]
qSort [] = []
qSort [x] = [x]
qSort (x:xs) = qSort less ++ [x] ++ qSort more
  where (less, more) = partition (< x) xs

qSort' :: Ord a => [a] -> [a]
qSort' [] = []
qSort' [x] = [x]
qSort' all@(x:_) = qSort less ++ qSort more
  where (less, more) = partition (< x) all

assert (qSort [5, 4, 3, 2, 1] == [1, 2, 3, 4, 5])
assert (qSort' [5, 4, 3, 2, 1] == [1, 2, 3, 4, 5])