primesUpTo' num (l:ls) = l : primesUpTo' num (filter (\x -> x `mod` l /= 0) ls)
primesUpTo' num (l:ls) = l : primesUpTo' num (filter (\x -> x `mod` l /= 0) ls)
primesUpTo' num (l:ls) = l : primesUpTo' num (filter (\x -> x `mod` l /= 0) ls)