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Hello,
   I have a problem loading a mesh with isolated vertices. In the 
polyhedron_scan_off.h there is a call to function 
remove_unconnected_vertices() based on the of HalfedgeDS::Supports_removal's 
value type(Tag_true/Tag_false). I presume that I have to activate this type 
with something like typedef CGAL::Tag_true Supports_removal but I'm a newbie 
with CGAL and I have not a clearly idea where I have to put this code's line. 
My mesh definition is:

template <class Refs, class T, class P>
class MyHalfedge : public CGAL::HalfedgeDS_vertex_base<Refs, T, P>
{
protected:
        typedef CGAL::Tag_true Supports_removal;
};

template <class Refs, class T, class P, class Norm>
class My_vertex : public CGAL::HalfedgeDS_vertex_base<Refs, T, P> {
        Norm  norm;
public:
        typedef CGAL::Tag_true Supports_removal;

        My_vertex() {} // repeat mandatory constructors
        My_vertex( const P& pt) : CGAL::HalfedgeDS_vertex_base<Refs, T, 
P>(pt) {}
        typedef Norm Normal_3;
        Normal_3&       normal()       { return norm; }
        const Normal_3& normal() const { return norm; }
};

template <class Refs, class T, class Norm>
class My_facet : public CGAL::HalfedgeDS_face_base<Refs, T> {
        Norm  norm;
public:
        // no constructors to repeat, since only default constructor mandatory
        typedef Norm Normal_3;
        Normal_3&       normal()       { return norm; }
        const Normal_3& normal() const { return norm; }
};

struct My_items : public CGAL::Polyhedron_items_3 {
        template <class Refs, class Traits>
        struct Vertex_wrapper {
                typedef typename Traits::Point_3  Point;
                typedef typename Traits::Vector_3 Normal;
                typedef My_vertex<Refs, CGAL::Tag_true, Point, Normal> Vertex;
        };
        template <class Refs, class Traits>
        struct Face_wrapper {
                typedef typename Traits::Vector_3 Normal;
                typedef My_facet<Refs, CGAL::Tag_true, Normal> Face;
        };
};


typedef CGAL::Simple_cartesian<double>                 Kernel;
typedef Kernel::Point_3                                Point_3;
typedef CGAL::Polyhedron_3<Kernel, My_items, CGAL::HalfedgeDS_vector> 
MyCGALMesh; 

Can you help me?

Thanks, Guido.