isprime.cpp

#include <iostream>

template <int N, int M>
struct is_factor {
  static const bool value = N % M == 0;
};

template <int N, int M>
struct divide_test {
  static const bool value = !is_factor<N, M>::value && divide_test<N, M-1>::value;
};

template <int N>
struct divide_test<N, 1> {
  static const bool value = true;
};

template <int N>
struct is_prime {
  static const bool value = divide_test<N, N-1>::value;
};

int main() {
  if (is_prime<23>::value) {
    std::cout << "Prime!" << std::endl;
  } else {
    std::cout << "Not prime!" << std::endl;
  }
}