#include <iostream>
#include <map>

class Coord {
    public:
        Coord ( int x, int y );
        bool operator< ( const Coord &r ) const;
        int x;
        int y;
};

Coord::Coord ( int x, int y ) : x(x), y(y)
{
}

bool Coord::operator< ( const Coord &r ) const
{
    return ( this->x < r.x && this->y < r.y );
    // Or you could try this
    /*
    return ( this->x < r.x || ( this->x == r.x && this->y < r.y ) );
    // if you try that, the output will be correct, but 2,51 will be smaller
    // than 77,37, which it isn't supposed to be.
    */
}

int main () {
    Coord test1(2,51);
    Coord test2(77,37);
    std::map<Coord, int> testmap;
    testmap[test1] = 1;
    testmap[test2] = 2;
    std::map<Coord, int>::iterator it;
    for(it=testmap.begin(); it!=testmap.end(); it++){
        std::cout << (it->first).x << "," << (it->first).y << ": ";
        std::cout << it->second << "\n";
    }
    // Result is:
    // 2,51: 2
    //
    // Nothing else.
    return 0;
}