CGAL 5.1.3  2D Boolean Operations on Nef Polygons Embedded on the Sphere

#include <CGAL/Nef_polyhedron_S2.h>
A sloop is a great circle on a sphere.
A shalfloop is an oriented sloop. It is always paired with a shalfloop whose supporting Sphere_circle
is pointing in the opposite direction. The twin()
member function returns this shalfloop of opposite orientation. Each Nef_polyhedron_S2
can only have one sloop (resp. two shalfloops).
The figure below depicts the relationship between a shalfloop and sfaces on a sphere map.
There is no need for a user to create a SHalfloop
explicitly. The class Nef_polyhedron_S2<Traits>
manages the needed shalfloops internally.
Types  
The following types are the same as in  
typedef unspecified_type  Mark 
type of mark.  
typedef unspecified_type  Sphere_circle 
sphere circle type stored in SHalfloop.  
typedef unspecified_type  SHalfloop_const_handle 
const handle to SHalfloop.  
typedef unspecified_type  SFace_const_handle 
const handle to SFace.  
Operations  
const Mark &  mark () const 
the mark of the halfloop.  
const Sphere_circle &  circle () const 
the sphere circle of the halfloop.  
SHalfloop_const_handle  twin () const 
the twin of the halfloop.  
SFace_const_handle  incident_sface () const 
the incident sface of the halfloop.  