Example of a recursive factorial function

recursive-constexpr.cpp

#include <array>
#include <cstdint>
#include <cstdio>

constexpr std::uint64_t factorial(std::uint64_t n) {
  // Recursion termination condition
  if (n == 0) 
  {
    return 1;
  }
  return n * factorial(n - 1);
}

void printFactorial(std::uint64_t n) 
{
   printf("%lu!=%lu\n", n, factorial(n));
}

constexpr std::array num{16ull, 9ull};
int main() {
  printFactorial(5);

  for (const int n : num) 
  {
    printFactorial(n);
  }
}