7.12.3.5 The isnormal macro
Synopsis
#include <math.h>
int isnormal(real-floating x);
Description
The isnormal macro determines whether its argument value is normal (neither zero, subnormal, infinite, nor NaN). First, an argument represented in a format wider than its semantic type is converted to its semantic type. Then determination is based on the type of the argument.
Returns
The isnormal macro returns a nonzero value if and only if its argument has a normal value.