[Qgis-developer] isfinite <-> std::isfinite

[Gavin Macaulay]

Marco,

Good point about using numeric_limits instead of the C99 isfinite. I'll
change the offending code to use numeric_limits (and move it to QgsRect
where it better belongs)

Thanks

Gavin


> humarco wrote:
>> Dear developers,
>>
>> in qgswmsprovider.cpp:1954, there are the following lines of code. I
>> have gcc
>> version 4.0.3 and this version needs 'std::isfinite' to compile.
>
> Marco,
>
> It's very strange libstdc++ puts isfinite to std namespace.
> isinfinite is *not* in C++ standard, as well as not in C98.
> This macro (as well as isnormal,isnan,isinf, etc.) is defined in C99
> standard. C++ standard does not define them (is based on C98).
>
> As I see in libstdc++ sources, this macro is wrapped by free function.
> In libstdc++ 3.x, it's in global namespace, but in libstdc++ 4.x, it's
> defined in std::, but it's *marked* in sources as an extension.
>
> So, isfinite or std::isfinite is *not* portable function,
> it's an extension.
>
>> I wonder
>> from what version on it needs 'isfinite' without 'std::' . Please post
>> your
>> compiler versions and if you need 'std::isfinite' or 'isfinite' for it.
>>
>> #if __GNUC__ >= 4
>>
>> if(!isfinite(extent.xMin()) || !isfinite((int)extent.yMin()) ||
>> !isfinite(extent.xMax()) ||
>> \
>>        !isfinite((int)extent.yMax()))
>> #else
>>
>> if(!std::isfinite(extent.xMin()) || !std::isfinite((int)extent.yMin())
>> || !std::isfinite(extent.xMax()) ||
>> \
>>        !std::isfinite((int)extent.yMax()))
>> #endif
>
> Isn't it better to use std::numeric_limits<T> [1] to check
> numeric ranges?
> Less code and better portability:
>
> if (extent.yMax() <= std::numeric_limits<double>::max()) {}
>
> There is also test for infinity support for given type possible:
>
> if (std::numeric_limits<double>::has_infinity
> {
>     if (some_value == std::numeric_limits<double>::infinity())
>    {
>       // some_value is infinite
>    }
> }
>
>
> [1] http://www.dinkumware.com/manuals/?manual=compleat&page=limits2.html
>
> Cheers
> --
> Mateusz Loskot
> http://mateusz.loskot.net
> _______________________________________________
> Qgis-developer mailing list
> Qgis-developer at lists.qgis.org
> http://lists.qgis.org/cgi-bin/mailman/listinfo/qgis-developer
>