#include <iostream>
using namespace std;

class Point2D {
    int x, y;
public:
    Point2D(int xx = 0, int yy = 0) : x(xx), y(yy) {}
    int getX() const { return x; }
    int getY() const { return y; }
};

class LexCompare {					      // lex comparison
public:
    int operator()(const Point2D& p1, const Point2D& p2) const
    {
        if      (p1.getX() < p2.getX()) return -1; // first compare x
        else if (p1.getX() > p2.getX()) return +1;
        else if (p1.getY() < p2.getY()) return -1; // x's equal; compare y
        else if (p1.getY() > p2.getY()) return +1;
        else 					         return 0; // both x and y are equal
    }
};

template <typename Key, typename Comp>
class GenericClass
{
    Comp comp;					// comparator object
// ...
public:
    void memberFunction(Key p, Key q)
    {
        if (comp(p, q) > 0)      cout << "p > q" << endl; // compare keys using comp
        else if (comp(p, q) < 0) cout << "p > q" << endl
        else                     cout << "p = q" << endl;
    }
};

int main()
{
    Point2D p, q(1, 0);					// p and q are points
    GenericClass<Point2D, LexCompare> concrete;
    concrete.memberFunction(p, q);     // compare p, q using LexCompare
    return 0;
}