Re: [Boost-testing] serialization - NaN, +/Inf and others

From: Caleb Epstein (caleb.epstein_at_[hidden])
Date: 2005-11-17 14:52:36

On 11/17/05, Robert Ramey <ramey_at_[hidden]> wrote:
>
> The problem is given something like +/inf how do I create a float with
> that value?
>  Can I use something like this?
>  double x;
> x = std::numeric_limits<T>::quiet_NaN();
>  assert(x == std::numeric_limits<T>::quiet_NaN());
>

Not sure why you'd need the check if you've just done the assignment, but I
don't believe that NaN-ness and Inf-ness can be tested like that. You'd can
use isnan() (which is spelled _isnan on Windows) to test for NaN. Not sure
if there is any way to distinguish between signaling and non-signaling NaNs
however. BSD-derived systems provide an isinf() as well, but Windows seems
to omit this one. There is also the C99 fpclassify stuff others have alluded
to. Win32 has _fpclass it would seem.

--
Caleb Epstein
caleb dot epstein at gmail dot com