CGAL 5.6.1  2D and 3D Linear Geometry Kernel

AdaptableBinaryFunction
Operations  
Comparison_result  operator() (const Kernel::Point_2 &p, const Kernel::Point_2 &q) 
Compares the Cartesian coordinates of points p and q lexicographically in \( yx\) order: first \( y\)coordinates are compared, if they are equal, \( x\)coordinates are compared.  