[Development] Changing qreal to a float

Marc Mutz marc.mutz at kdab.com
Tue Feb 21 10:02:24 CET 2012

On Tuesday February 21 2012, André Somers wrote:
> Op 21-2-2012 9:35, Thiago Macieira schreef:
> > On terça-feira, 21 de fevereiro de 2012 08.24.52, Samuel Rødal wrote:
> >> Also, I guess we'll want convenience functions "QRectD QRectF::toRectD()
> >> const" etc. Can that be done with the typedefs proposed above, or does
> >> it require having "QRectD QRectD::toRectD() const" as well?
> >
> > With some template magic it can be done.
> >
> > If you write:
> > template<class t>  class QBasicRect;
> > typedef QBasicRect<float>  QRectF;
> > typedef QBasicRect<double>  QRectD;
> >
> > Then you can't specialise QBasicRect<float or double>  anymore. You can
> > only use the default expansion or partial specialisations that are yet to
> > be written. That means it's easier to add an "constexpr inline QRectD
> > toRectD() const;" to all classes than to just the float and integer ones.
> >
> > But someone really motivated can add more magic using QEnableIf.
> Just wondering: while I think using templates for these classes is a
> good idea in principle, will using such template magic as you are
> suggesting here hurt compilation times, both of Qt itself and Qt
> applications using these classes?

One would disallow compilers to instantiate the template with C++11 extern 
templates (this would be a good idea for all templates, esp. those with 
arguments constrained to just a few potential types). All other compilers: 
who cares? :)


Marc Mutz <marc.mutz at kdab.com> | Senior Software Engineer
KDAB (Deutschland) GmbH & Co.KG, a KDAB Group Company
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