isnan

   Test for a NaN. Returns 1 if the argument is NaN; 0 if not.

   This function is supported on OpenVMS Integrity servers and
   Alpha only.

   Format

     #include  <math.h>

     int isnan  (double x);

     int isnanf  (float x);

     int isnanl  (long double x);
 

Additional information available:

Argument        Description