How to overload unary minus operator in C++?

Question

I\'m implementing vector class and I need to get an opposite of some vector. Is it possible to define this method using operator overloading?

Here\'s what I mean:

Answer 1

It's

Vector2f operator-(const Vector2f& in) {
   return Vector2f(-in.x,-in.y);
}

Can be within the class, or outside. My sample is in namespace scope.