Main recursion

Updated on 2021-11-13

The main() function in C++ is just a function and can be used like any other function. It is only special in that it is called by the operating systems and has the command line arguments passed to it. However, it is still possible to call main() while the program is running. For example, here is a program that computes factorials by recursively calling main().

#include <cassert>
#include <cstdlib>
#include <iostream>

// Recursive main!
int main(int argc, char **argv) {
  if (argv == nullptr) {
    if (argc == 0) return 1;
    return argc * main(argc - 1, nullptr);
  } else {
    int result = main(std::atoi(argv[1]), nullptr);
    std::cout << result << std::endl;
    return 0;
  }
}