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## CGAL::Triangulation_cw_ccw_2

### Definition

The class Triangulation_cw_ccw_2 offer two functions int cw(int i) and int ccw(int i) which given the index of a vertex in a face compute the index of the next vertex of the same face in clockwise or counterclockwise order. This works also for neighbor indexes. Thus, for example the neighbor neighbor(cw(i)) of a face f is the neighbor which is next to neighbor(i) turning clockwise around f. The face neighbor(cw(i)) is also the first face encountered after f when turning clockwise around vertex i of f.

Many of the classes in the triangulation package inherit from Triangulation_cw_ccw_2. This is for instance the case for CGAL::Triangulation_2<Traits,Tds>::Face. Thus, for example the neighbor neighbor(cw(i)) of a face f is the neighbor which is next to neighbor(i) turning clockwise around f. The face neighbor(cw(i)) is also the first face encountered after f when turning clockwise around vertex i of f.

Figure: Vertices and neighbors.

#include <CGAL/Triangulation_2.h>

### Creation

Triangulation_cw_ccw_2 a;
| default constructor.

### Operations

int | a.ccw ( const int i)
|  | returns the index of the neighbor or vertex that is next to the neighbor or vertex with index i in counterclockwise order around a face.
int | a.cw ( const int i)
|  | returns the index of the neighbor or vertex that is next to the neighbor or vertex with index i in counterclockwise order around a face.

### See Also

CGAL::Triangulation_2<Traits,Tds>
CGAL::TriangulationDSFace_2

Next: Triangulation_euclidean_traits_2<K>

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The CGAL Project . Tue, December 21, 2004 .