CGAL 5.1.1  dD Geometry Kernel

Operations  
bool  operator() (const Kernel_d::Point_d &p, const Kernel_d::Point_d &q) 
returns true iff p is lexicographically smaller than q with respect to Cartesian lexicographic order of points. More...  
bool Kernel_d::Less_lexicographically_d::operator()  (  const Kernel_d::Point_d &  p, 
const Kernel_d::Point_d &  q  
) 
returns true
iff p
is lexicographically smaller than q
with respect to Cartesian lexicographic order of points.
p
and q
have the same dimension.