CGAL users discussion list

[Matthew Denno <>]

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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