[Lemon-devel] Math constants in C++

[Alpár Jüttner]

Hi,

What about something like this?

http://lime.cs.elte.hu/~alpar/hgwebdir.cgi/lemon/rev/3a6cdebbb855

It does not emit a warning - at least on my computer.

Regards,
Alpar

On Mon, 2008-02-04 at 09:53 +0000, Alpár Jüttner wrote:
> > Why do we have lemon::dim2?
> 
> The only reason is to enable us to also have 3 dimensional points in to
> future. In fact, lemon::dim2::Point used to be called lemon::xy and the
> 3dim version would have been called lemon::xyz. These names worked well,
> they do not conform to our conventions. Then another idea was to call
> them  Xy, but it looked very stupid. Thus came the namespace dim2 (and
> possibly dim3 in the future).
> 
> >  I think if we have lemon::dim2 for Point, 
> > BoundingBox, etc., then we should have lemon::math for constants.
> 
> If we want to provide any alternative declaration for PI in the future,
> then of course we should. :)
> 
> Regards,
> Alpar
> 
> 
> > Alpár Jüttner írta:
> > > Hi,
> > > 
> > >>  >       * Is that OK to declare all these constants as 'const long
> > >>  >         double'?
> > >> Does it cause warnings, e.g. in 'double x = 2 * PI;'?
> > > 
> > > Could you investigate the answer for this?
> > > 
> > >>  >       * Do we need to provide all of the original math.h constants for
> > >>  >         'compatibility'?
> > >>
> > >> I don't think so, I suggest only the ones that are used in LEMON or that
> > >> are really important for another reason. (E.g. E is important even if it
> > >> is not used in LEMON yet.)
> > > 
> > > In fact E _is_ used in lemon. (That is why I faced with this whole
> > > problem.)
> > > The constants in math.h are PI, E and SQRT2, LN2, , LN10, LOG2E, LOG10E,
> > > (which seem to be reasonably important) and the reciprocal of some of
> > > them (hopefully we don't need them because of optimization).
> > > 
> > >> What about a separate namespace, e.g. lemon::math (or lemon::constants)?
> > >> I think lemon::math::PI, lemon::math::E would be very good.
> > > 
> > > Yes, they look good. But are they better in any aspect then lemon:PI and
> > > lemon:E?
> > > 
> > >> What about prefix 'C_'?
> > > 
> > > The only reason why namespaces exist in C++ is to avoid all these kind
> > > of prefixes.
> > > 
> > > Regars,
> > > Alpar
> > > 
> > > _______________________________________________
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> > > Lemon-devel at lemon.cs.elte.hu
> > > http://lemon.cs.elte.hu/mailman/listinfo/lemon-devel
> > 
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