CGAL users discussion list

[Kwok Jasper <>]

Thank you very much

> From:
> To:
> Date: Thu, 22 Jan 2009 15:49:07 +0100
> Subject: Re: [cgal-discuss] about the function incident_vertices() and output iterator
>
> 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/
>
> --
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