CGAL users discussion list

["Laurent Rineau (GeometryFactory)" <>]

On Thursday 22 January 2009 15:30:21 Kwok Jasper wrote:
> Thank you very much
>
> and for the following for calling the incident_vertices function
>
> > > typedef CGAL::Exact_predicates_inexact_constructions_kernel K1;
> > > typedef CGAL::Delaunay_triangulation_3<K1> Triangulation;
> > > typedef Triangulation::Point Point_tr;
> > >
> > > Triangulation Tr;
> > >
> > > Vertex_handle v =  Tr.insert(Point_tr(0,0,0));
> > >  Tr.insert(Point_tr(40,20,10));
> > >                                              //...insert some more
> > > points
> > >
> > >     vector<Vertex_handle> con;
> > >     con.resize(800);
> > >
> > >     vector <Vertex_handle>::iterator start_inci = con.begin();
> > >     vector<Vertex_handle>::iterator end_inci = con.end();
> > >     vector<Vertex_handle>::iterator curr_inci;
> > >
> > >      for(curr_inci = start_inci; curr_inci != end_inci; ++curr_inci)
> > >      {
> > >             //do sth with the vertex handles.
> > >      }
>
> may I ask if it is a proper way to use it.
> In the method , I use     con.resize(800);
> If I didn't use the resize() function there.
> then it have a exception telling that the iterator cannot be deferenced
> May I ask if the above code is a proper way to use the incident_vertices()

Hi,

The above code does not use incident_vertices() at all!

To fill a vector, you do not really need to use resize. The function 
vector<T>::push_back(T) adds an element at the end of the vector, and 
increases it size.

The usual way to use incident_vertices is the following:

#include <iterators>

// create an empty vector
std::vector<Vertex_handle> container;

t.incident_vertices(v, std::back_inserter(container));
// 'container' now contains handles for all vertices incident to 'v'

std::back_inserter is a function from the STL that creates a special "output 
iterator" from a container. That output iterator internaly calls 'push_back'.

-- 
Laurent Rineau, PhD
Engineer at GeometryFactory
http://www.geometryfactory.com/