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["Sebastien Loriot (GeometryFactory)" <>]

Michele wrote:
> Dear all, 
> I have implemented a code that prints the points and the vertices of the
> faces of a triangulation, the code is attacted, with using three different
> methods: vertex circulator, face circulator and face iterator. 
> Both vertex circulator and face iterator show the good result, but it is not
> true for the face circulator, why? 
> Could someone explain me the reasons? 
> Thank you. 
I am not sure to understand what you want to do with your code.
A FOO_circulator does not print all FOO of the triangulation but
only incident FOO to a vertex.

In your case
Face_circulator fc = t.incident_faces(t.infinite_vertex())
takes all faces incident to the infinite_vertex and consider
all facets incident to the infinite_vertex. Thus, one of the
vertex of each such faces is the infinite vertex
(the one with strange coordinates). Adding a
if (!t.is_infinite(fc)) before printing would avoid this illegal use of
point() of the infinite_vertex.

If you want to iterate over all the finite faces of the triangulation
use Finite_faces_iterator and finite_faces_begin/finite_faces_end
(same for vertices and edges)
as documented here:
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Triangulation_2_ref/Class_Triangulation_2.html#Cross_link_anchor_1296

Also remember that an edge is a std::pair<Face_handle,int> (the edge of 
a face f which is opposed to the vertex indexed i) as documented here:

http://www.cgal.org/Manual/latest/doc_html/cgal_manual/TDS_2_ref/Concept_TriangulationDataStructure_2.html#Cross_link_anchor_1307

S.

> Michele Quinto 
>
> This is the output of my code. 
>
> print the points belong to triangulation 
> 2 2 
> 2 1 
> 2 0 
> 1 0 
> 0 0 
> 0 1 
> 0 2 
> 1 2 
> print the faces belong to triangulation (face circulator) 
> triangle: 6.93721e-310 3.45846e-323 2 2 2 1 
> triangle: 6.93721e-310 3.45846e-323 2 1 2 0 
> triangle: 6.93721e-310 3.45846e-323 2 0 1 0 
> triangle: 0 0 6.93721e-310 3.45846e-323 1 0 
> triangle: 0 0 0 1 6.93721e-310 3.45846e-323 
> triangle: 0 1 0 2 6.93721e-310 3.45846e-323 
> triangle: 6.93721e-310 3.45846e-323 0 2 1 2 
> triangle: 6.93721e-310 3.45846e-323 1 2 2 2 
> print the faces belong to triangulation (faces iterator) 
> triangle: 0 2 0 1 1 0 
> triangle: 0 1 0 0 1 0 
> triangle: 1 1 0 2 1 0 
> triangle: 1 2 0 2 1 1 
> triangle: 2 0 1 2 1 1 
> triangle: 1 0 2 0 1 1 
> triangle: 2 1 1 2 2 0 
> triangle: 2 2 1 2 2 1 
>
>
>
> #include <CGAL/Exact_predicates_inexact_constructions_kernel.h> 
> #include <CGAL/Triangulation_2.h> 
>
> typedef CGAL::Exact_predicates_inexact_constructions_kernel K; 
> typedef CGAL::Triangulation_2<K> Triangulation; 
> typedef Triangulation::Vertex_circulator Vertex_circulator; 
> typedef Triangulation::Face_circulator Face_circulator; 
> typedef Triangulation::Vertex_iterator Vertex_iterator; 
> typedef Triangulation::Face_iterator Face_iterator; 
> typedef Triangulation::Point Point; 
>
> int main(int argc, char *argv[]) 
> { 
>         int i, j; 
>         Triangulation t; 
>         
>         for(i=0; i<3; i++) 
>                 for(j=0;j<3;j++) 
>                         t.insert(Point((double)i,(double)j)); 
>         std::cout<<"print the points belong to triangulation"<<std::endl; 
>         Vertex_circulator vc = t.incident_vertices(t.infinite_vertex()),
> done(vc); 
>         if(vc!=0) 
>                 { 
>                         do{ 
>                                 std::cout<< vc->point() <<std::endl; 
>                         }while(++vc!=done); 
>                 } 
>         std::cout<<"print the faces belong to triangulation (face
> circulator)"<<std::endl; 
>         Face_circulator fc = t.incident_faces(t.infinite_vertex()),
> done2(fc); 
>         if(fc!=0) 
>                 { 
>                 do{ 
>                         std::cout<<"triangle: " 
>                                         <<fc->vertex(0)->point()<<"\t"
> <<fc->vertex(1)->point()<<"\t"<<fc->vertex(2)->point()<<std::endl; 
>                         }while(++fc!=done2); 
>                 } 
>         std::cout<<"print the faces belong to triangulation (faces
> iterator)"<<std::endl; 
>         Face_iterator fi=t.finite_faces_begin(); 
>         for(;fi!=t.finite_faces_end();fi++) 
>                 { 
>                 std::cout<<"triangle: " 
>                                         <<fi->vertex(0)->point()<<"\t"
> <<fi->vertex(1)->point()<<"\t"<<fi->vertex(2)->point()<<std::endl; 
>                 } 
> return 0; 
> }  
>