isnan

isnan

Test for floating-point NaN

Portability: C99

   #include <math.h>

   int isnan(floating x);

isnan tests whether its argument is a NaN.

isnan returns zero if its argument is not a NaN, and a non-zero value otherwise.

When called from a compilation compiled without the bfp option, isnan always returns zero.

fpclassify, isfinite, isinf, isnormal

"Mathematical Functions" in Chapter 2, "Function Categories"