overload operator = with two arguments in c++

Question

i'm writing a class like this :

class Digit
{
    private :
        int *ref;
    public :
        Digit (int a) : ref(&a) {}
        int get_val ()
        {
            return (*ref);
        }
        Digit operator= (int &a)
        {
            if (a < 0 || a > 9)
                throw "invalid digit assignment.";
            (*ref) = a;
            return (*this);
        }
    };

so if someone define a digit ,he can not assign value more than 9 or less than 0 to it. the problem is, i also want to define another = operator, that he can assign a Digit to some value too. i tried something like this :

int operator= (int &a, Digit &d)
{
    a = d.get_value();
    return a;
}

but i get some error : 'int operator=(int&, Digit&)' must be a nonstatic member function

how can i fix this? how can i overload operator = with 2 arguments?

Answer 1

What you really need may be operator int().

class Digit {
   operator int() { return get_val(); }
};

Then you can write int a = d; assuming d is of class Digit.