\( \newcommand{\E}{\mathrm{E}} \) \( \newcommand{\A}{\mathrm{A}} \) \( \newcommand{\R}{\mathrm{R}} \) \( \newcommand{\N}{\mathrm{N}} \) \( \newcommand{\Q}{\mathrm{Q}} \) \( \newcommand{\Z}{\mathrm{Z}} \) \( \def\ccSum #1#2#3{ \sum_{#1}^{#2}{#3} } \def\ccProd #1#2#3{ \sum_{#1}^{#2}{#3} }\)

CGAL 4.8 - Halfedge Data Structures

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CGAL::HalfedgeDS_items_2 Class Reference
Item Classes

`#include <CGAL/HalfedgeDS_items_2.h>`

## Definition

The class `HalfedgeDS_items_2` is a model of the `HalfedgeDSItems` concept.

It uses the default types for vertices, halfedges, and faces that declare all incidences supported by a `HalfedgeDS`. The vertex also contains a point of type `Traits::Point_2`, where `Traits` is the template argument of the corresponding `HalfedgeDS`.

Is Model Of:
  `HalfedgeDSItems`

See Also
  `CGAL::HalfedgeDS_min_items`
  `CGAL::Polyhedron_items_3`
  `HalfedgeDS<Traits,Items,Alloc>`
  `PolyhedronItems_3`
  `CGAL::HalfedgeDS_vertex_base<Refs>`
  `CGAL::HalfedgeDS_halfedge_base<Refs>`
  `CGAL::HalfedgeDS_face_base<Refs>`

Example

The following example shows the canonical implementation of the `HalfedgeDS_items_2` class. It uses the base classes for the item types that are provided in the library.

struct HalfedgeDS_items_2 {
template < class Refs, class Traits>
struct Vertex_wrapper {
typedef typename Traits::Point_2 Point;
typedef CGAL::HalfedgeDS_vertex_base< Refs, Tag_true, Point> Vertex;
};
template < class Refs, class Traits>
struct Halfedge_wrapper {
typedef CGAL::HalfedgeDS_halfedge_base< Refs> Halfedge;
};
template < class Refs, class Traits>
struct Face_wrapper {
typedef CGAL::HalfedgeDS_face_base< Refs> Face;
};
};

The following example shows a class definition for a new items class derived from the `HalfedgeDS_items_2` class. It replaces the `Face_wrapper` with a new definition of a face that contains a member variable for color. The new face makes use of the face base class provided in the library.

// A face type with a color member variable.
template <class Refs>
struct My_face : public CGAL::HalfedgeDS_face_base<Refs> {
CGAL::Color color;
My_face() {}
My_face( CGAL::Color c) : color(c) {}
};
// An items type using my face.
struct My_items : public CGAL::HalfedgeDS_items_2 {
template <class Refs, class Traits>
struct Face_wrapper {
typedef My_face<Refs> Face;
};
};

Examples:
  HalfedgeDS/hds_prog_color.cpp, HalfedgeDS/hds_prog_compact.cpp, and HalfedgeDS/hds_prog_compact2.cpp.