demo_overloading_increment_operator.cc

#include <iostream>
#include <string>

struct Person {
  size_t age = 0;
  std::string name;

  Person& operator++() {    // prefix
    ++age;
    return *this;
  }
  Person operator++(int) {  // postfix
    Person res = *this;     // trivial copy-constructor is called
    this->operator++();
    return res;
  }

  // not necessary here, but necessary for classes whose private members are about to be printed.
  friend std::ostream& operator<<(std::ostream& os, const Person& p);
};

std::ostream& operator<<(std::ostream& os, const Person& p) {
  return os << p.name << '\t' << p.age;
}

int main() {
  Person liam;
  liam.name = "Liam Huang";

  std::cout << liam << '\n';
  std::cout << ++liam << '\n';
  std::cout << liam++ << '\n';
  std::cout << liam << '\n';

  return 0;
}