C++ Compile-time factorial calculation

fact.cpp

#include <iostream>

template <uint64_t n>
struct Fact {
  static const uint64_t value = n * Fact<n - 1>::value;
};

template <>
struct Fact<1> {
  static const uint64_t value = 1;
};

constexpr uint64_t fact(uint64_t n) { return n == 1 ? 1 : n * fact(n - 1); }

int main() {
  std::cout << Fact<20>::value << std::endl;
  std::cout << fact(20) << std::endl;
}