CGAL users discussion list

[Matthew Denno <>]

Thanks for the clarification.  I figured that once I convert my results to double precision for output to shapefile they will no longer be exact.  I need the intermediate results to be exact so that my algorithms work properly, but think that converting to an approximate solution just before writing the output will be okay.

On Wed, Oct 21, 2009 at 9:47 AM, Laurent Rineau (GeometryFactory) <> wrote:

On Wednesday 21 October 2009 15:41:03 Matthew Denno wrote:
> Ah, perfect!  Thank you.
>
> On Wed, Oct 21, 2009 at 9:33 AM, Laurent Rineau (GeometryFactory) <
>
> > wrote:
> > On Wednesday 21 October 2009 15:11:47 Matthew Denno wrote:
> > > 1) Is there a way to convert a CGAL::Lazy_exact_nt<CGAL::Gmpq> value to
> > > double precision so that I can write to results out to a shapefile?
> >
> > As for that question, use CGAL::to_double
> >
> > http://www.cgal.org/Manual/3.5/doc_html/cgal_manual/Algebraic_foundations
> >_ref/Function_to_double.html

I send the mail too quickly. Be aware that the "conversion" done by
CGAL::to_double might not be exact. If you convert a CGAL::Gmpq or a
CGAL::Lazy_exact_nt<CGAL::Gmpq>, the CGAL::to_double function template returns
an approximation of the number, with the best precision possible with the type
"double".

--

Laurent Rineau, PhD
R&D Engineer at GeometryFactory           http://www.geometryfactory.com/
Release Manager of the CGAL Project       http://www.cgal.org/
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