Class Data Encapsulation(private data) in operator overloading

Question

Below is the code

The Code:

#include 
using namespace std;

class Rational {
  int num;  // numerator
  int den;  // den         


        

Answer 1

Why C++ allow the parameter to access private data outside of the class ? Is it some kind of a special case?

The rule with access specifiers is:
"Access specifiers apply to per class and not per object"
So, You can always access private members of a class object in member function of that class.

A copy constructor/copy assignment operator are commonly used examples of the rule though we do not notice it that often.

Online Sample:

class Myclass
{
    int i;
    public:
       Myclass(){}
       Myclass(Myclass const &obj3)
       { 
            //Note i is private member but still accessible
            this->i = obj3.i;
       }
};

int main()
{
    Myclass obj;
    Myclass obj2(obj);
}

Good Read:
What are access specifiers? Should I inherit with private, protected or public?