CGAL users discussion list

[Marc Mörig <>]

Dear CGAL maintainers,

in the file Sqrt_extension_type.h, there is the following code:

std::pair<double, double> compute_to_interval() const
{
  if (! is_extended_)
      return CGAL_NTS to_interval(a0_);
  CGAL::Interval_nt<false>::Protector p;
  const CGAL::Interval_nt<false>&  a0_int = CGAL_NTS to_interval(a0_);
  const CGAL::Interval_nt<false>&  a1_int = CGAL_NTS to_interval(a1_);
  const CGAL::Interval_nt<false>&  root_int = CGAL_NTS to_interval(root_);
  const CGAL::Interval_nt<false>&  x_int =
      a0_int + (a1_int * CGAL::sqrt(root_int));

  std::pair<double, double> res(x_int.inf(), x_int.sup());
  this->update_cached_value(res);
  return res;
}


The Protector p sets a directed rounding mode for floating point 
arithmetic, which is propagated to other code inside, e.g. 
to_interval(a0_). In my case, this breaks code which assumes the default 
rounding mode.

Should I consider this a bug or a feature? It is easily fixable in CGAL 
though.

Regards,
Marc Mörig

--
Marc Mörig                                 Email:  

Institut für Simulation und Graphik        Phone: +49 391 67-52858
Otto-von-Guericke Universität Magdeburg    Office:         G29-227