CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

I see.

I think it's a bug, because the protector should be placed just before 
const CGAL::Interval_nt<false>& x_int=...

Can you check and tell me if it's working then.

Sebastien.

On 07/26/2012 09:35 AM, Marc Mörig wrote:
> On 07/26/2012 09:24 AM, Sebastien Loriot (GeometryFactory) wrote:
> > On 07/26/2012 09:09 AM, Marc Mörig wrote:
> > > 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.
> > Are you sure the problems is coming from that part? The previous
> > rounding mode mode is restored when the protector is deleted.
> >
> > Sebastien.
>
> I am pretty sure. a0_ is of a custom number type I wrote myself. Hence
> the directed rounding mode is in effect when my code is called. The
> problem goes away if I move the Protector creation three lines
> downwards. This is ok, since no floating-point operations are performed
> in the interval assignment anyways.
>
> Marc