what is the difference between overloading an operator inside or outside a class?

Question

In C++, i know there are two ways to overload. We can overload it inside (like class a) or outside (like class b). But, the question is, is there any d

Answer 1

The member operator+ requires the LHS to be an a - The free operator requires LHS or RHS to be a b and the other side to be convertible to b

struct Foo {
    Foo() {}
    Foo(int) {}
    Foo operator+(Foo const & R) { return Foo(); }
};


struct Bar {
    Bar() {}
    Bar(int) {}
};

Bar operator+(Bar const & L, Bar const & R) {
    return Bar();
}


int main() {
    Foo f;
    f+1;  // Will work - the int converts to Foo
    1+f;  // Won't work - no matching operator
    Bar b;
    b+1;  // Will work - the int converts to Bar
    1+b;  // Will work, the int converts to a Bar for use in operator+

}