C++11 dice rolling syntax: write 2d6 dice roll as 2_d6 c++ syntax

dice.cpp

#include <iostream>
#include <cstdlib>

int roll_dice(int numdice, int die) {
  int total = 0;
  for (int i = 0; i < numdice; i++) {
    total += std::rand() % die;
  }
  return total;
}

// Reference: http://en.cppreference.com/w/cpp/language/user_literal
int operator "" _d4(unsigned long long N) { return roll_dice(N, 4); }
int operator "" _d6(unsigned long long N) { return roll_dice(N, 6); }
int operator "" _d8(unsigned long long N) { return roll_dice(N, 8); }

int main() {
  std::srand(std::time(0));
  std::cout << "2d6 + 3 = " << 2_d6 + 3 << std::endl;
  std::cout << "5d4 + 1 = " << 5_d4 + 1 << std::endl;
}