 
default constructor.

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

 checks whether the vertex lies at infinity and not associated with a point with bounded coordinates.  

 checks whether the vertex is isolated (i.e., has no incident edges).  

 returns the number of edges incident to v.  


returns a circulator circulator that allows going over the halfedges
incident to v (that have v as their target).
The edges are traversed in a clockwise direction around v.
 


returns a handle to the face that contains v in its interior.
 

 returns whether the $$xcoordinate of the vertex is finite or whether it lies at $$ ± .  

 returns whether the $$ycoordinate of the vertex is finite or whether it lies at $$ ± .  


returns the point associated with the vertex.
