CGAL users discussion list

[David Keller <>]

Hi,

Thank you for the fast response. I have just discovered another problem 
with IO of Arrangement_2: Unbounded and fictitious faces are apparently 
not correctly reconstructed when read. The problem is illustrated on a 
slightly changed io.cpp from examples/Arrangement_2/io.cpp which you 
find attached to this mail.

Kind regards,
David Keller


 wrote:
> Hi David,
>
> Thank you for all this. The first 2 patches have been already applied 
> to the internal release and will be included in the next public release.
>
> I was able to reproduce the problem in the 3rd item below with 
> Exact_predicates_exact_constructions_kernel and even with arrangement 
> (without history). We'll are looking into it.
>
> Regarding your question, equal_2_object() should return true if and 
> only if the graphs of the curves are the same. It's a good point, and 
> we'll add it to the documentation.
>
> Quoting David Keller 
> <>:
>
> > Hi,
> >
> > I have some issues with Arrangement_with_history_2:
> >
> >   1. operator== in Arr_with_history_2_functions.h misses a return value
> >      for the case of non-self-assignments. Attached is a patch
> >      (arr_with_hist_return_value.patch) which fixes the problem for me.
> >   2. If VERBOSE is defined there are several issues with
> >      function-name-lookups in derived objects leading to compile-time
> >      errors (at least for gcc 4.0 and later). Attached is a patch
> >      (sweep_line_debug.patch) to fix this problem.
> >   3. Inserting an overlapping but "not equal" curve in an
> >      Arrangement_with_history_2 leads to a runtime-error (precondition
> >      failure in Arrangement_2_functions.h at line 1579). Attached is a
> >      reproducer (arr_with_history_overlapping_curves.cpp). What should
> >      traits::equal_2_object() implement here: Equal graph or equal
> >      representation? The case may actually be rare. However, I'm not
> >      quite sure if the current implementation gives the desired
> >      behavior. If so, it would possibly be a good choice to mention
> >      this in the documentation.
> >
> > Thanks and kind regards
> > David Keller
> > --
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//! \file examples/Arrangement_2/ex_io.cpp
// Using the arrangement I/O operators.

#include "arr_rational_nt.h"
#include <CGAL/Cartesian.h>
#include <CGAL/Arr_segment_traits_2.h>
#include <CGAL/Arrangement_2.h>
#include <CGAL/IO/Arr_iostream.h>
#include <fstream>

#include "point_location_utils.h"

typedef CGAL::Cartesian<Number_type>                  Kernel;
typedef CGAL::Arr_segment_traits_2<Kernel>            Traits_2;
typedef CGAL::Arrangement_2<Traits_2>                 Arrangement_2;

int main ()
{
  // Construct the arrangement.
  Arrangement_2    arr;

  construct_segments_arr (arr);

  std::cout << "Writing an arrangement of size:" << std::endl
            << "   V = " << arr.number_of_vertices()
            << ",  E = " << arr.number_of_edges()
            << ",  F = " << arr.number_of_faces() << std::endl;

  // Write the arrangement to a file.
  std::ofstream    out_file ("arr_ex_io.dat");

  out_file << arr;
  out_file.close();

  // Read the arrangement from the file.
  Arrangement_2    arr2;
  std::ifstream    in_file ("arr_ex_io.dat");

  in_file >> arr2;
  in_file.close();

  std::cout << "Read an arrangement of size:" << std::endl
            << "   V = " << arr2.number_of_vertices()
            << ",  E = " << arr2.number_of_edges()
            << ",  F = " << arr2.number_of_faces() << std::endl;

  if ( arr.number_of_unbounded_faces() != arr2.number_of_unbounded_faces() ) 
  {
    std::cerr << "Number of unbounded faces is not equal" << std::endl;
    return (-1);
  }

  return (0);
}