Operator "<<" overloading return type

Suppose there is a cPoint class.

class cPoint {
  int x, y, z;
};

I wanted to print all of three variables in a single statement. So, I overloaded operator << just like

   friend std::ostream& operator<< (std::ostream &cout, cPoint &p);

   std::ostream& operator<< (std::ostream &out, cPoint &p) {
     out << p.get_x() << " " << p.get_y() << " " << p.get_z() << std::endl;
     return out;
   }

Make sense?

My question lies in the lines of that what would happen in case of insertion operator(>>). I overloaded that as well to take the values of x, y and z into a single statement.

    friend std::istream& operator>> (std::istream &cin, Point &p);

    std::istream& operator>> (std::istream &in, Point &p) {
        int tmp;
        in >> tmp;
        p.set_x(tmp);
        in >> tmp;
        p.set_y(tmp);
        in >> tmp;
        p.set_z(tmp);
    }

Clear?

int main() {
  cout << p << endl;
  cin >> p;
}

I know that if operator<< returned void then the compiler evaluates cout << p << endl; Due to the precedence/associativity rules, it evaluates this expression as (cout << cPoint) << endl;. cout << cPoint calls our void-returning overloaded operator<< function, which returns void. Then the partially evaluated expression becomes: void << endl;, which makes no sense!

But what would happen in case of >>. Why can't I return a void for >> as like:

    void operator>> (std::istream &cin, Point &p);

Because it does not matter if cin >> p returns void or something else. There is no other operand who could use it. This is not clear.

---

You can return void from stream extracting operator >> , just like you can return void from a stream inserting operator << . And just like with the inserting one, it will prevent you from doing chaining:

cPoint p, q;
cin >> p >> q; // This would fail with return type void

... and the very common test-correctness idiom:

cPoint p;
if (cin >> p) {
}

---

I overloaded operator << just like ...

Proper override should take the second parameter by const reference:

friend std::ostream& operator<< (std::ostream &cout, const cPoint &p);
//                                                   ^^^^^

I overloaded that as well to take the values of x, y and z into a single statement.

You forgot to return in from the implementation:

std::istream& operator>> (std::istream &in, Point &p) {
    int tmp;
    in >> tmp;
    p.set_x(tmp);
    in >> tmp;
    p.set_y(tmp);
    in >> tmp;
    p.set_z(tmp);
    return in; <<== Here
}

Making it void would prevent you from reading anything else after the point on the same line.

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