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[Josip Dzolonga <>]

I was referring to this

while(!seen.empty()) {

          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);

                    break;
                }
          }
}

I break the loop after a point is removed. I also tried the code that you provided, but that unfortunately did not solve the problem.

Best,
Josip

On Sun, Nov 15, 2009 at 10:08 PM, Andreas Fabri <> wrote:

Hi Josip,

I am not sure you understood my explanantion, but it can also be
that I didn't understand yours.

It is a mistake to do the ++vit, AFTER having called T.remove(vit),
and that is what your for loop does.

My version makes a copy of thr iterator, advances the iterator
and only then removes the vertex.

andreas


Josip Dzolonga wrote:

Hi Andreas,

I corrected myself in my latest reply, but that did not solve the problem.

Josip

On Sun, Nov 15, 2009 at 9:07 PM, Andreas Fabri < <mailto:>> wrote:

   Hi Josip,

   You shouldn't expect that ++vit works correctly after that you called
   T.remove(vit).

   You better write this


   for(Finite_vertices_iterator vit = T.finite_vertices_begin();
                   vit != T.finite_vertices_end();) {

                   if(seen.find(vit->point()) != seen.end()) {
                       seen.erase(vit->point());
                       Vertex_handle vh = vit;
                       ++vit;
                       T.remove(vh);
                       break;
                   }
             }


   Note that the same would be true for a std::list.

   andreas

   Josip Dzolonga wrote:

       Hi Nico,

       I thought of that, but at no point I am reusing old cell
       handles/vertex handles. I thought that while removing them, I
       might be causing the problem - but even if I change to code to
       the following, the problems remains

       while(!seen.empty()) {
                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);
                          break;
                      }
                }
       }

       That is, I am iterating again over all vertices.

       Thanks,
       Josip

       On Sun, Nov 15, 2009 at 8:42 PM, Nico Kruithof
       < <mailto:>

       <mailto: <mailto:>>>

       wrote:

          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
       < <mailto:>

          <mailto: <mailto:>>> 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





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