faktorial 0 = 1
faktorial 1 = 1
faktorial n = if (n < 0)
  then error "ArgumentError: Negative argument"
  else (*) n (faktorial ((-) n 1))

ahoj = 3

--- fibonaci
fib 0 = 1
fib 1 = 1
fib n =  (+) (fib (n-1)) (fib (n-2))

fib' n = f 0 1 n
  where
    f x _ 0 = x
    f x y n = f y (x + y) (n - 1)

spoj [] ys = ys
spoj (x:xs) ys = x:(spoj xs ys)


obrat [] = []
obrat (x:xs) = spoj (obrat xs) [x]

filtrujsuda = filter even

quicksort [] = []
quicksort (x:xs) = (quicksort (filter (<x) xs))++[x]++(quicksort (filter (>x) xs))