[Inkscape-devel] Re: isnan

isnan unfortunately isn't part of the C++ standard.

Availability of isnan, std::isnan, _isnan and friends can vary according to whether <math.h> has been #included (perhaps indirectly such as by C-based libraries that we use) and whether <cmath> has been #included (perhaps indirectly such as by standard C++ headers that we #include).

We may need to write our own isnan.h header.

Does anyone know whether `x != x' is a portable definition of isnan?

(`(libc)FP Comparison Functions' says that `!=' doesn't raise an exception for NaN in IEEE arithmetic, btw.)

pjrm.