Function operator-

libs/geometry/point2d.hpp:160–163

template <typename T>
Point<T> operator-(Point<T> const & a, Point<T> const & b)
{
  return Point<T>(a.x - b.x, a.y - b.y);
}

template <typename T>
Point<T> operator+(Point<T> const & a, Point<T> const & b)