独自挿入子の作成

#include < iostream >
using namespace std;

class coord {
    int x, y;
public:
    coord() { x = 0; y = 0; }
    coord(int i, int j){ x= i; y = j; }
    friend ostream &operator<<(ostream &stream, coord ob);
};

ostream &operator<<(ostream &stream, coord ob)
{
    stream << ob.x << ", " << ob.y << '\n';
    return stream;
}
int main()
{
    coord a(1, 1), b(10, 23);
    cout << a << b;
    
    return 0;
}