Implementing 64-bit Mersenne Twister - definitions

I am learning C++, trying to generate a few random numbers within a specified range.

I'm trying to implement this answer here on SO, and revise it for it to be able to generate 64-bit integer.

Which I basically succeeded in, basic program could look like:

#include <iostream>
#include <random>

unsigned long long int random_integer(unsigned long long int rand_min, unsigned long long int rand_max)
{

    // initialize = seed the random device
    std::random_device random_device;

    // use Mersenne Twister as random-number generator engine
    std::mt19937_64 random_number_generator(random_device());

    // number distribution, guaranteed unbiased
    std::uniform_int_distribution<unsigned long long int> number_distribution(rand_min, rand_max);

    return number_distribution(random_number_generator);

}

int main()
{
    for (int i = 1; i <= 10; i++)
    {
        std::cout << random_integer(10000000, 100000000) << std::endl;
    }
    return 0;
}

Questions:

• should I define the random device:

  std::random_device random_device
  
  

  out of the function?

• I am also unsure where to define the Mersenne Twister:

  std::mt19937_64 random_number_generator(random_device());
  
  

  for the function to work as expected.