add asVector distanceSquare distanceTo get isDegenerate isEqualTo kInvalid kOrigin length negate offset offset operator!= operator* operator* operator* operator* operator*= operator*= operator+ operator+ operator+ operator+= operator+= operator- operator- operator- operator-= operator/ operator/= operator== Point2d Point2d Point2d polarPoint rulerPoint rulerPoint scaleBy scaleBy set set subtract subtract transform x y

operator+ Point2d operator+ ( const Vector2d &  vec, const Point2d &  pnt  ) friend 用矢量平移, 矢量 + 点 = 点