#include <iostream>
#include <vector>
 
class Myclass {
public: 
  Myclass() : a(1.0) {}
 
  float a;
  float &a_ref = a;
 
  void addOne() {
    a = a + 1.0;
  }
};
 
int main() {
  Myclass instance1;
  instance1.addOne();
 
  //prints 2:
  std::cout << "instance.a_ref is " << instance1.a_ref << std::endl;
 
  std::vector<Myclass> vec;
  Myclass instance2;
  vec.push_back(instance2);
 
  vec.at(0).addOne();
 
  //prints 1;
  std::cout << "vec.at(0).a_ref is " << vec.at(0).a_ref << std::endl;
 
  std::cout << "vec.at(0).a_ref points to " << &vec.at(0).a_ref << std::endl;
  std::cout << "instance2.a lives at " << &instance2.a << std::endl;
  return 0;
}

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