text: 
  
  #ifndef TCG_EDGE_H
  #define TCG_EDGE_H
  
  // STD includes
  #include "assert.h"
  
  namespace tcg
  {
  
  template <typename E>
  struct edge_traits {
  	typedef typename E::vertices_const_iterator vertices_const_iterator;
  	typedef typename E::vertices_iterator vertices_iterator;
  
  	typedef typename E::faces_const_iterator faces_const_iterator;
  	typedef typename E::faces_iterator faces_iterator;
  };
  
  //-------------------------------------------------------------------------------
  
  class Edge
  {
  public:
  	typedef const int *vertices_const_iterator;
  	typedef int *vertices_iterator;
  
  	typedef const int *faces_const_iterator;
  	typedef int *faces_iterator;
  
  protected:
  	int m_v[2];
  	int m_f[2];
  	int m_index;
  
  public:
  	Edge() : m_index(-1)
  	{
  		m_v[0] = -1, m_v[1] = -1;
  		m_f[0] = -1, m_f[1] = -1;
  	}
  	Edge(int v1, int v2) : m_index(-1)
  	{
  		m_v[0] = v1, m_v[1] = v2;
  		m_f[0] = -1, m_f[1] = -1;
  	}
  	~Edge() {}
  
  	void setIndex(int idx) { m_index = idx; }
  	int getIndex() const { return m_index; }
  
  	int vertex(int i) const { return m_v[i]; }
  	int verticesCount() const { return m_v[0] < 0 ? 0 : m_v[1] < 0 ? 1 : 2; }
  	int otherVertex(int v) const { return m_v[0] == v ? m_v[1] : m_v[0]; }
  
  	void addVertex(int v)
  	{
  		assert(verticesCount() < 2);
  		m_v[verticesCount()] = v;
  	}
  	void setVertex(int i, int v) { assert(i < verticesCount()), m_v[i] = v; }
  	vertices_iterator eraseVertex(vertices_iterator it)
  	{
  		*std::copy(it + 1, verticesEnd(), it) = -1;
  		return it;
  	}
  
  	vertices_const_iterator verticesBegin() const { return m_v; }
  	vertices_const_iterator verticesEnd() const { return m_v + verticesCount(); }
  	vertices_iterator verticesBegin() { return m_v; }
  	vertices_iterator verticesEnd() { return m_v + verticesCount(); }
  
  	int face(int i) const { return m_f[i]; }
  	int facesCount() const { return m_f[0] < 0 ? 0 : m_f[1] < 0 ? 1 : 2; }
  	int otherFace(int f) const { return m_f[0] == f ? m_f[1] : m_f[0]; }
  
  	void addFace(int f)
  	{
  		assert(facesCount() < 2);
  		m_f[facesCount()] = f;
  	}
  	void setFace(int i, int f) { assert(i < facesCount()), m_f[i] = f; }
  	faces_iterator eraseFace(faces_iterator it)
  	{
  		*std::copy(it + 1, facesEnd(), it) = -1;
  		return it;
  	}
  
  	faces_const_iterator facesBegin() const { return m_f; }
  	faces_const_iterator facesEnd() const { return m_f + facesCount(); }
  	faces_iterator facesBegin() { return m_f; }
  	faces_iterator facesEnd() { return m_f + facesCount(); }
  };
  
  } // namespace tcg
  
  #endif // TCG_EDGE_H
  