[Lemon-devel] Math constants in C++

[Kovács Péter]

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?

Sorry, but I don't know exactly the gcc warning options and I don't know 
other important C++ compilers (e.g. Visual C++).

 >> 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?

Why do we have lemon::dim2? I think if we have lemon::dim2 for Point, 
BoundingBox, etc., then we should have lemon::math for constants.

Regards,
Peter

P.S. What solutions are used by other cross-platform libraries?

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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