-- Easy
function is_even(num)
   return num % 2 == 0
end

function is_prime(num)
   local res = true
   for i = 2,num-1 do
      if num % i == 0 then
         res = false
      end
   end
   return res
end

function print_first_n_primes(n)
   local p = 1
   while n ~= 0 do
      repeat
         p = p+1
      until is_prime(p)
      print(p)
      n = n-1
   end
end

-- Medium
function for_loop(a, b, f)
   while a < b do
      f(a)
      a = a+1
   end
end

-- Hard
function reduce(max, init, f)
   local tmp = init
   for i = 1,max do
      tmp = f(tmp, i)
   end
   return tmp
end

function factorial(n)
   return reduce(n, 1, function(x,y) return x*y end)
end