Halfedges are sotred in doublyconnected lists and form chains. These chains define the inner and outer boundaries of connceted components.
 
default constructor.

All nonconst methods listed below also have const counterparts that return constant handles, iterators or circulators:

 returns whether the halfedge is fictitious (i.e., connects two vertices at infinity and is not associated with a valid curve).  

 returns a handle for the source vertex of e.  

 returns a handle for the target vertex of e.  

 returns whether the source vertex of e lies at infinity.  

 returns whether the target vertex of e lies at infinity.  

 returns the direction of the halfedge: SMALLER if e's source vertex is lexicographically smaller than it target (so the halfedge is directed from left to right), and LARGER if it is lexicographically larger than the target (so the halfedge is directed from right to left).  

 returns the face that e is incident to (The face lies to the left of e).  

 returns the twin halfedge.  

 returns e's predecessor in the connected component it belongs to.  

 returns e's successor in the connected component it belongs to.  

 returns a circulator that allows traversing the halfedges of the connected component boundary (CCB) that contains e. The circulator is initialized to point to e.  
 

returns the $$xmonotone curve associated with e.
