text: // Copyright (c) 2006 Foundation for Research and Technology-Hellas (Greece).
  // All rights reserved.
  //
  // This file is part of CGAL (www.cgal.org).
  // You can redistribute it and/or modify it under the terms of the GNU
  // General Public License as published by the Free Software Foundation,
  // either version 3 of the License, or (at your option) any later version.
  //
  // Licensees holding a valid commercial license may use this file in
  // accordance with the commercial license agreement provided with the software.
  //
  // This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
  // WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  //
  // $URL$
  // $Id$
  // 
  //
  // Author(s)     : Menelaos Karavelas <mkaravel@iacm.forth.gr>
  
  #ifndef CGAL_VORONOI_DIAGRAM_2_APOLLONIUS_GRAPH_DEGENERACY_TESTERS_H
  #define CGAL_VORONOI_DIAGRAM_2_APOLLONIUS_GRAPH_DEGENERACY_TESTERS_H 1
  
  #include <CGAL/Voronoi_diagram_2/basic.h>
  #include <CGAL/Voronoi_diagram_2/Adaptation_traits_base_2.h>
  #include <CGAL/Voronoi_diagram_2/Identity_rejectors.h>
  #include <CGAL/Triangulation_utils_2.h>
  
  namespace CGAL {
  
  namespace VoronoiDiagram_2 { namespace Internal {
  
  //=========================================================================
  //=========================================================================
  
  template<class DG>
  class Apollonius_graph_edge_tester_2
    : public Rejector_base
  {
    // tests whether a dual edge has zero length
   public:
    typedef DG                                       Delaunay_graph;
  
    typedef typename DG::Edge                        Edge;
    typedef typename DG::Face_handle                 Face_handle;
    typedef typename DG::Edge_circulator             Edge_circulator;
    typedef typename DG::All_edges_iterator          All_edges_iterator;
    typedef typename DG::Finite_edges_iterator       Finite_edges_iterator;
  
    typedef bool           result_type;
  
   private:
    typedef Triangulation_cw_ccw_2                     CW_CCW_2;
  
    typedef typename Delaunay_graph::Geom_traits       Geom_traits;
  
    typedef typename Delaunay_graph::Vertex_handle     Vertex_handle;
  
    typedef typename Geom_traits::Site_2               Site_2;
  
   public:
    bool operator()(const Delaunay_graph& dual,
  		  const Face_handle& f, int i) const
    {
      if ( dual.dimension() == 1 ) { return false; }
  
      if ( dual.is_infinite(f, i) ) { return false; }
  
      Vertex_handle v3 = f->vertex(     i  );
      Vertex_handle v4 = dual.data_structure().mirror_vertex(f, i);
  
      if ( dual.is_infinite(v3) || dual.is_infinite(v4) ) {
        return false;
      }
  
      Vertex_handle v1 = f->vertex( CW_CCW_2::ccw(i) );
      Vertex_handle v2 = f->vertex( CW_CCW_2::cw(i) );
  
      Site_2 s1 = v1->site();
      Site_2 s2 = v2->site();
      Site_2 s3 = v3->site();
      Site_2 s4 = v4->site();
      return dual.geom_traits().is_degenerate_edge_2_object()(s1,s2,s3,s4);
    }
  
    bool operator()(const Delaunay_graph& dual, const Edge& e) const {
      return operator()(dual, e.first, e.second);
    }
  
    bool operator()(const Delaunay_graph& dual,
  		  const All_edges_iterator& eit) const {
      return operator()(dual, *eit);
    }
  
    bool operator()(const Delaunay_graph& dual,
  		  const Finite_edges_iterator& eit) const {
      return operator()(dual, *eit);
    }
  
    bool operator()(const Delaunay_graph& dual,
  		  const Edge_circulator& ec) const {
      return operator()(dual, *ec);
    }
  };
  
  
  //=========================================================================
  //=========================================================================
  
  } } //namespace VoronoiDiagram_2::Internal
  
  } //namespace CGAL
  
  #endif // CGAL_VORONOI_DIAGRAM_2_APOLLONIUS_GRAPH_DEGENERACY_TESTERS_H
  