CGAL users discussion list

[Nico Kruithof <>]

Hi Josip,

The assertion says that the vertex is not contained in the Cell. When you remove vertices, cells get removed and added when re-triangulating. Internally, CGAL will reuse the memory of deleted cells for the new cells. This might be the reason you are getting the assertion. 

-- Nico

On Sun, Nov 15, 2009 at 6:26 PM, Josip Dzolonga <> wrote:

Hello everyone,

I am trying to remove some certain points from the Delaunay triangulation. I had some problems even before, and got some advice from here, but the problem still pertains. The problematic code follows

for(Finite_vertices_iterator vit = T.finite_vertices_begin();
            vit != T.finite_vertices_end(); ++vit) {
            if(seen.find(vit->point()) != seen.end()) {
                seen.erase(vit->point());
                T.remove(vit);
           }
}

Where seen is of type std::set<Point> and has been already filled. Later on when I try to use the triangulation, I get the following error

CGAL error: assertion violation!
Expr: v == V[3]
File: /usr/include/CGAL/Triangulation_ds_cell_base_3.h
Line: 98
terminate called after throwing an instance of 'std::logic_error'
  what():  basic_string::_S_construct NULL not valid
Aborted

Which comes from the function  int index(const Vertex_handle& v). I can not remove the same vertex twice, since I am iterating over the finite vertices and this is the only place where vertex removal is taking place. Any ideas would be highly appreciated!

Best,
Josip