CGAL users discussion list

[Ben Supnik <>]

You can't use arrangement_2 with an inexact constructions kernel, which 
is what cartesian double is.  Version of CGAL doesn't matter, an extact 
constructions kernel is a requirement for the arrangement 2 package in 
all the versions I know of!

Ben Strasser wrote:
> Hello,
>
> the following program crashes for me:
>
> #include <CGAL/Cartesian.h>
> #include <CGAL/Arrangement_2.h>
> #include <CGAL/Arr_segment_traits_2.h>
>
> typedef CGAL::Cartesian<double>                Kernel;
> typedef CGAL::Point_2<Kernel>                Point;
> typedef CGAL::Segment_2<Kernel>                Segment;
> typedef CGAL::Ray_2<Kernel>                    Ray;
> typedef CGAL::Vector_2<Kernel>                Vector;
> typedef CGAL::Arrangement_2<CGAL::Arr_segment_traits_2<Kernel> >
>                                            Arrangement;
>
> int main(){
>    Arrangement arr;
>    CGAL::insert_curve(arr, Segment(Point(1.11414, 0.292881), 
> Point(4.13119, 1.29114)));
>    CGAL::insert_curve(arr, Segment(Point(1.11414, 0.292881), 
> Point(4.29535, 0.61658)));
>    CGAL::insert_curve(arr, Segment(Point(1.11414, 0.292881), 
> Point(4.16702, 0.269299)));
>    CGAL::insert_curve(arr, Segment(Point(1.11414, 0.292881), 
> Point(1.48276, -0.458071)));
> }
>
> The output is
>
> CGAL error: precondition violation!
> Expr: _locate_around_vertex (_vertex(prev->target()), cv, MAX_END) == 
> _halfedge(prev)
> File: /usr/include/CGAL/Arrangement_2/Arrangement_2_functions.h
> Line: 1047
> Explanation:In the clockwise order of curves around the vertex, cv must 
> succeed the curve of prev.
> terminate called after throwing an instance of 
> 'CGAL::Precondition_exception'
>  what():  CGAL ERROR: precondition violation!
> Expr: _locate_around_vertex (_vertex(prev->target()), cv, MAX_END) == 
> _halfedge(prev)
> File: /usr/include/CGAL/Arrangement_2/Arrangement_2_functions.h
> Line: 1047
> Explanation: In the clockwise order of curves around the vertex, cv must 
> succeed the curve of prev.
> Aborted
>
> I compile with
> g++ -O2 bug.cpp -lCGAL -o prog
>
> my compiler version is
> g++ (Ubuntu 4.3.2-1ubuntu12) 4.3.2
>
> What am I doing wrong?
>
> I am uncertain as to what my exact cgal version is as I installed it 
> through the package system. The package version is
> 3.3.1-2ubuntu1 (interpid)
> I know it's not the newest version, however I'd hate to install cgal 
> from the sources just to find out, that the code above still doesn't 
> work. Could anyone please check if the code above works with newer 
> versions?
>
> Thanks for your time,
> Ben Strasser

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