CGAL users discussion list

I am still waiting for help... the last thing I post is a reply to Mr. Fabri:

Andreas Fabri wrote:
>There is a global function left_vertex_2(Polygon_2)
>and a member function Polygon_2::left_vertex

And I said:
sorry but I didn't understand... you mean:
xMin = left_vertex_2( pgn ); ??
or:
xMin = pgn.left_vertex(); ??

for the first I get:
VVc_demo.cpp: In function `bool read_polygons(const char*, Polygons_list_2&, 
Bbox_2&)':
VVc_demo.cpp:623: error: no matching function for call to `left_vertex_2(
Rat_polygon_2&)'

and for the latter I get:
VVc_demo.cpp: In function `bool read_polygons(const char*, Polygons_list_2&, 
Bbox_2&)':
VVc_demo.cpp:623: error: cannot convert `

__gnu_cxx::__normal_iterator<CGAL::Point_2<CGAL::Simple_cartesian<Rational> 
>*, std::vector<CGAL::Point_2<CGAL::Simple_cartesian<Rational> >, 
std::allocator<CGAL::Point_2<CGAL::Simple_cartesian<Rational> > > > >' to `



I forgot to say that pgn is defined like this:
typedef VVc_diagram_2::Rat_polygon_2          Rat_polygon_2;
Rat_polygon_2               pgn (vertices.begin(), vertices.end());

and in VVc_diagram_2 class I have:
typedef Partial_polygon_Voronoi_diagram_2<Traits_2>          Partial_pvd_2;
typedef typename Partial_pvd_2::Rat_polygon_2                Rat_polygon_2;


and in Partial_polygon_Voronoi_diagram_2 class I have:
typedef Traits_                                Traits_2;
typedef typename Traits_2::Rat_kernel          Rat_kernel;
typedef Polygon_2<Rat_kernel>                  Rat_polygon_2;

So what should I do?
Mahmood NT