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% | Reference manual page: TriangulationDSVertexBase_2.tex
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% | 13.08.2003   Author
% | Package: Package
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\RCSdef{\RCSTriangulationDSVertexBaseRev}{$Id$}
\RCSdefDate{\RCSTriangulationDSVertexBaseDate}{$Date$}
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\begin{ccRefConcept}{TriangulationDSVertexBase_2}

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\ccDefinition
  
The concept \ccRefName\ describes the requirements for the
vertex base class of a \ccc{Triangulation_data_structure_2<Vb,Fb>}.

Note that if  the \ccc{Triangulation_data_structure_2} 
is plugged  into a triangulation class, 
the vertex base class has additional geometric
requirements depending on the triangulation class.

At the base level,  
provides access to one of its incident
face through a \ccc{Face_handle}.

Since the \ccc{Triangulation_data_structure_2} is the class 
which defines the handle
types, the vertex base class has to be somehow 
parameterized by the triangulation
data structure.  But since the \ccc{Triangulation_data_structure_2}
itself is parameterized by the face and vertex
base classes, there is a cycle in the definition of these classes.  
In order
to break the cycle, the base classes for faces and vertices
 which are plugged in to instantiate a
\ccc{Triangulation_data_structure_2}
use a \ccc{void} as triangulation
data structure parameter. Then,
the \ccc{Triangulation_data_structure_2}
uses a {\it rebind}  mechanism (similar to the one specified in
\ccc{std::allocator}) in order to plug itself 
as parameter in the face and vertex  base classes. 
This mechanism requires that the base class  provides
a templated nested class \ccc{Rebind_TDS} that
itself provides 
the subtype \ccc{Rebind_TDS<TDS2>::Other}
which is the {\it rebound} version of the base class.
 This {\it rebound} base class is  the class
that the   \ccc{Triangulation_data_structure_2}
 actually  uses  as a base class for the class
of \ccc{Triangulation_data_structure_2::Vertex}.



\ccRefines{\ccc{TriangulationDataStructure_2::Vertex}}


\ccTypes
\ccThree{typedef TriangulationDataStructure_2::Vertex_handle}{}{}
\ccThreeToTwo
The concept \ccRefName\ has to provide the following types.

\ccNestedType{
  template <typename TDS2>
  struct Rebind_TDS;}
{This nested template class has to define a type \ccc{Other} which is the
{\it rebound} vertex base , where the actual 
\ccc{Triangulation_data_structure_2} is  plugged in.
This type  \ccc{Other}  will be the actual base
of the class \ccc{Triangulation_data_structure_2::Vertex}.}


\ccTypedef{typedef TriangulationDataStructure_2 Triangulation_data_structure;}{}
\ccGlue
\ccTypedef{typedef TriangulationDataStructure_2::Vertex_handle Vertex_handle;}{}
\ccGlue
\ccTypedef{typedef TriangulationDataStructure_2::Face_handle Face_handle;}{}


\ccCreation
\ccCreationVariable{v}  %% choose variable name

\ccThree{Vertex_handle}{Facetxxxxxxxxxxxxxxxxxxxxxxxxx}{}

\ccConstructor{TriangulationDSVertexBase_2();}{default constructor.}
\ccGlue
\ccConstructor{TriangulationDSVertexBase_2(Face_handle f);}
{Constructs a vertex pointing to face  \ccc{f}.}


\ccHeading{Various}

\ccMethod{void * for_compact_container() const;}{}
\ccGlue
\ccMethod{void * & for_compact_container();}{}
{ These member functions are required by \ccc{Triangulation_data_structure_2}
  because it uses \ccc{Compact_container} to store its faces.  See the
  documentation of \ccc{Compact_container} for the exact requirements.}


\ccHasModels

\ccc{CGAL::Triangulation_ds_vertex_base_2<Tds>}\\
\ccc{CGAL::Triangulation_vertex_base_2<Traits,Vb>}\\
\ccc{CGAL::Regular_triangulation_vertex_base_2<Traits,Vb>} \\
\ccc{CGAL::Triangulation_hierarchy_vertex_base_2<Vb>} \\
\ccc{CGAL::Triangulation_vertex_base_with_info_2<Info,Traits,vb>}

\ccSeeAlso
\ccc{TriangulationVertexBase_2}\\
\ccc{TriangulationDSFaceBase_2}\\
\ccc{TriangulationFaceBase_2} \\
\ccc{TriangulationDataStructure_2::Vertex} \\
\ccc{Triangulation_data_structure_2<Vb,Fb>} \\


\end{ccRefConcept}

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