## ApolloniusGraphHierarchyVertexBase_2

### Definition

The vertex of an Apollonius graph included in an Apollonius graph hierarchy has to provide some pointers to the corresponding vertices in the graphs of the next and preceeding levels. Therefore, the concept ApolloniusGraphHierarchyVertexBase_2 refines the concept ApolloniusGraphVertexBase_2, by adding two vertex handles to the correponding vertices for the next and previous level graphs.

### Refines

ApolloniusGraphVertexBase_2

### Types

ApolloniusGraphHierarchyVertexBase_2 does not introduce any types in addition to those of ApolloniusGraphVertexBase_2.

### Creation

ApolloniusGraphHierarchyVertexBase_2 v;
| Default constructor.
ApolloniusGraphHierarchyVertexBase_2 v ( Site_2 s);
| Constructs a vertex associated with the site s and embedded at the center of s.
ApolloniusGraphHierarchyVertexBase_2 v ( Site_2 s, Face_handle f);
| Constructs a vertex associated with the site s, embedded at the center of s, and pointing to face f.

### Operations

Vertex_handle | v.up () | Returns a handle to the corresponding vertex of the next level Apollonius graph. If such a vertex does not exist Vertex_handle(NULL) is returned.
Vertex_handle | v.down () | Returns a handle to the corresponding vertex of the previous level Apollonius graph.
void | v.set_up ( Vertex_handle u)
|  | Sets the handle for the vertex of the next level Apollonius graph.
void | v.set_down ( Vertex_handle d)
|  | Sets the handle for the vertex of the previous level Apollonius graph;

### Has Models

CGAL::Apollonius_graph_hierarchy_vertex_base_2<CGAL::Apollonius_graph_vertex_base_2<Gt,StoreHidden> >

### See Also

ApolloniusGraphDataStructure_2
ApolloniusGraphVertexBase_2
CGAL::Apollonius_graph_hierarchy_2<Gt,Agds>
CGAL::Triangulation_data_structure_2<Vb,Fb>
CGAL::Apollonius_graph_vertex_base_2<Gt,StoreHidden>
CGAL::Apollonius_graph_hierarchy_vertex_base_2<Agvb>