I have 3 short classes below. My question is also in the code below.

template< typename T >
class XY
{
public:
       XY() = default;
       XY(T x, T y) { vec2 = { x,y }; }
       virtual ~XY() = default;
       auto X() const -> T { return vec2[0]; }
       auto Y() const -> T { return vec2[1]; }
private:
       std::array<T, 2> vec2;
};

template< typename T >
class xy
{
public:
       xy() = default;
       xy(T xx, T yy) : x(xx), y(yy) {}
       virtual ~xy() = default;
       T x, y;
};
template<typename T>
class coordinates {
public:
       T _pp;
       void printcoordinates() {
              // how can I refer to _pp.x or _pp.X() when it T can be either XY or xy
              _pp.x or _pp.X();
              _pp.y or _pp.Y();
       }
};

}

I have 3 template classes, XY, xy, and coordinates. Please see the code snippets above, in coordinates, how can refer to XY.X() and xy.x?