namespace CGAL {

/*!
\ingroup PkgTDS3

The class `Triangulation_utils_3` defines operations on the indices of vertices 
and neighbors within a cell. 

\anchor Triangulation3figutils 
\image html utils.gif "Operations on indices."

*/

class Triangulation_utils_3 {
public:

/// \name Operations 
/// @{

/*! 
In dimension 3, index of the neighbor `n` that is next to the current cell, 
when turning positively around an oriented edge whose endpoints are 
indexed `i` and `j`. According to the usual numbering of 
vertices and neighbors in a given cell, it is also the index of the vertex 
opposite to this neighbor `n`. (see Figure \ref Triangulation3figutils). 
\pre `( i < 4 ) && ( j < 4 ) && ( i != j )`. 
*/ 
static unsigned int next_around_edge(unsigned int i, unsigned int j) const; 

/*! 
Has a meaning only in dimension 2. 

Computes the index of the vertex that is next to the vertex numbered 
`i` in counterclockwise direction. (see 
Figure \ref Triangulation3figutils). 
\pre `i<3`. 
*/ 
static unsigned int ccw(unsigned int i) const; 

/*! 
Same for clockwise. 
*/ 
static unsigned int cw(unsigned int i) const; 

/// @}

}; /* end Triangulation_utils_3 */
} /* end namespace CGAL */