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Hi.
I want to implement online removal of Sites for a Voronoi Diagram. So, since 
it
is not directly supported, I tried doing this using its dual - a delaunay
graph.

But I get an error.

/*previous declarations*/

// typedefs for defining the adaptor
typedef CGAL::Exact_predicates_inexact_constructions_kernel                  
K;
typedef CGAL::Delaunay_triangulation_2<K>                                   
DT;
typedef CGAL::Delaunay_triangulation_adaptation_traits_2<DT>                
AT;
typedef CGAL::Delaunay_triangulation_caching_degeneracy_removal_policy_2<DT>
AP;
typedef CGAL::Voronoi_diagram_2<DT,AT,AP>                                   
VD;

// typedef for the result type of the point location
typedef AT::Site_2                    Site_2;
typedef AT::Point_2                   Point_2;


/* This function call gives an error*/
void Vor_Map::set_pseudo_random() {
        typedef DT      Delaunay_graph;
        
        int capacity = noPoints/noSites;
        VD temp_vd = *vd;
        Delaunay_graph dual_ = temp_vd.dual();
        
        site_ext* s;//site_ext is a class derived from Site_2

       //this call just gives me the closest site in the Voronoi diagram to
this point
        s = (site_ext*)getSite(points[0].point, temp_vd);
        cout << s->x() << ":" <<  s->y() << endl;
        if ( s==NULL) cout<<"Errorr";
        dual_.remove((Site_2*)s);       
}



Error on the screen : 

20:17
CGAL error: assertion violation!
Expr: n == NULL
File: /usr/include/CGAL/Compact_container.h
Line: 681
Explanation:
terminate called after throwing an instance of 'CGAL::Assertion_exception'
  what():  CGAL ERROR: assertion violation!
Expr: n == NULL
File: /usr/include/CGAL/Compact_container.h
Line: 681
Aborted


Thanks in advance.

Navneet.