CGAL 5.5.1  2D and 3D Linear Geometry Kernel

AdaptableFunctor
(with four arguments) Operations  
Comparison_result  operator() (const Kernel::Point_2 &p, const Kernel::Point_2 &q, const Kernel::Point_2 &r, const Kernel::Point_2 &s) 
compares the signed distance of r and s to the directed line through p and q .  
Comparison_result  operator() (const Kernel::Line_2 &l, const Kernel::Point_2 &r, const Kernel::Point_2 &s) 
compares the signed distance of r and s to the directed line l .  