CGAL users discussion list

[Andreas Fabri <>]

Hi Matthew,

It's -> and not .  because f is a Face_handle and not a Face, and
a handle is something like a pointer.
http://www.cgal.org/Manual/3.4/doc_html/cgal_manual/Circulator_ref/Concept_Handle.html

Note that all iterators are also model of the concept Handle

andreas

Matthew Denno wrote:
> Thanks so much to both of you for your help.  I really appreciate you
> taking time to answer my novice questions as I learn.
>
> I think I am starting to learn my way around the documentation so that
> I can hopefully figure it out on my own in the future.
>
> One point of confusion for me still, which is probably more of a C++
> question than a specific CGAL question is why, for example, in the
> documentation it is shown as f.vertex() , but in code that was
> provided (and works) it is f -> vertex().  I suspect that in the
> documentation it is shown as f.vertex() to indicate that vertex() is a
> member of f but why is it accessed using f->vertex()?
>
> On Fri, Jun 12, 2009 at 8:14 AM, Andreas
> Fabri<>
>  wrote:
> > Hi Matthew,
> >
> > The triangulation is parameterized with a triangulation datastructure
> > which is parameterized with a vertex and face class.
> >
> >
> > ______________________________________________
> > Parameters
> > The class Triangulation_2<Traits,Tds> has two template parameters. The first
> > one Traits is the geometric traits, it is to be instantiated by a model of
> > the concept TriangulationTraits_2.
> >
> > The second parameter is the triangulation data structure, it has to be
> > instantiated by a model of the concept TriangulationDataStructure_2. By
> > default, the triangulation data structure is instantiated by
> > CGAL::Triangulation_data_structure_2 <
> > CGAL::Triangulation_vertex_base_2<Gt>, CGAL::Triangulation_face_base_2<Gt> >
> > > .
> >
> > Source:
> > http://www.cgal.org/Manual/3.4/doc_html/cgal_manual/Triangulation_2_ref/Class_Triangulation_2.html#Cross_link_anchor_1166
> > ______________________________________________
> >
> >
> > Whe you click on    CGAL::Triangulation_face_base_2<Gt>   you find
> >
> > ______________________________________________
> >
> > Is Model for the Concepts
> > TriangulationFaceBase_2
> >
> > http://www.cgal.org/Manual/3.4/doc_html/cgal_manual/Triangulation_2_ref/Class_Triangulation_face_base_2.html
> > ______________________________________________
> >
> >
> > "Model of a concept" means    implementations of a specification,
> > so when you click on   TriangulationFaceBase_2 and there on
> > TriangulationDSFaceBase_2
> >
> > you are one click away from what you search
> >
> > http://www.cgal.org/Manual/3.4/doc_html/cgal_manual/TDS_2_ref/Concept_TriangulationDSFaceBase_2.html#Cross_link_anchor_1178
> >
> >
> > The whole thing is rather decomposed, but it makes little sense to repeat
> > the documentation
> > of the concept for each model.
> >
> >
> > andreas
> >
> >
> >
> >
> > Matthew Denno wrote:
> > > Hi,
> > >
> > > I am hoping that someone can point me in the right direction to a
> > > solution for my problem.  I am new to both CGAL and C++ so I apologize
> > > if my questions should be obvious.
> > >
> > > I started out with one of the example problems.  After I have added
> > > the points to the Triangulation, I use a Face_iterator to iterate
> > > through the faces (I think through this part is ok).  The problem is I
> > > can't figure out how to access the verticies of each face as I iterate
> > > over them.
> > >
> > > If someone could point me in the right direction I would really
> > > appreciate it.  Maybe just a hint of what I should look for in the
> > > manual.
> > >
> > > The code I have been testing with is below.
> > >
> > > Thanks so much.
> > >
> > > Matt
> > >
> > > #include <fstream>
> > > #include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
> > > #include <CGAL/Triangulation_2.h>
> > >
> > > struct K : CGAL::Exact_predicates_inexact_constructions_kernel {};
> > >
> > > typedef CGAL::Triangulation_2<K>         Triangulation;
> > > typedef Triangulation::Vertex_circulator Vertex_circulator;
> > > typedef Triangulation::Point             Point;
> > > typedef Triangulation::Face_iterator     Face_iterator;
> > > typedef Triangulation::Vertex_handle     Vertex_handle;
> > > typedef Triangulation::Vertex_iterator   Vertex_iterator;
> > >
> > > int main() {
> > >  std::ifstream in("data/triangulation_prog1.cin");
> > >  std::istream_iterator<Point> begin(in);
> > >  std::istream_iterator<Point> end;
> > >
> > >  Triangulation t;
> > >  t.insert(begin, end);
> > >
> > >  for (Face_iterator fit = t.faces_begin();
> > >         fit != t.faces_end();
> > >         ++fit){
> > >
> > >        //This is where the problem is.
> > >        //print out the x and y coordinates of all three verticies of each
> > > face
> > >
> > >  }
> > >  return 0;
> > > }
> > --
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