## Prime numbers.

res = ''

def is_prime(n)
  if n < 2 then return false end  
  for i in 2..n
    if n % i == 0 then return false end
  end
  return true
end

def get_all_primes(n)
  for i in 0..n
    if is_prime(i)
		res += to_string(i) + ' '
	end
  end
end

get_all_primes(20)
assert(res == '2 3 5 7 11 13 17 19 ')