Operator Overloading in struct

Question

Suppose I define this structure:

struct Point {
   double x, y;
};

How can I overload the + operator so that, declared,

Answer 1

Here is how I would do it.

struct Point {
   double x, y;
   struct Point& operator+=(const Point& rhs) { x += rhs.x; y += rhs.y; return *this; }
   struct Point& operator+=(const double& k) { x += k; y += k; return *this; }
};

Point operator+(Point lhs, const Point& rhs) { return lhs += rhs; }
Point operator+(Point lhs, const double k) { return lhs += k; }
Point operator+(const double k, Point rhs) { return rhs += k; }