haskell_test

factors :: Int -> [Int]
factors n = [x | x <- [1..n], n `mod` x == 0]

prime :: Int -> Bool
prime n = factors n == [1, n]

primes :: Int -> [Int]
primes n = [x | x <- [2..n], prime x]

qsort :: Ord a => [a] -> [a]
qsort [] = []
qsort (x:xs) = qsort smaller ++ [x] ++ qsort larger
               where
                  smaller = [a | a <- xs, a <= x]
                  larger = [b | b <- xs, b > x]