isnan(x)
bool isnan (float x); bool isnan (double x); bool isnan (long double x);
int
float
double
long double
bool
true
false
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/* isnan example */ #include <stdio.h> /* printf */ #include <math.h> /* isnan, sqrt */ int main() { printf ("isnan(0.0) : %d\n",isnan(0.0)); printf ("isnan(1.0/0.0) : %d\n",isnan(1.0/0.0)); printf ("isnan(-1.0/0.0) : %d\n",isnan(-1.0/0.0)); printf ("isnan(sqrt(-1.0)): %d\n",isnan(sqrt(-1.0))); return 0; }
isnan(0.0) : 0 isnan(1.0/0.0) : 0 isnan(-1.0/0.0) : 0 isnan(sqrt(-1.0)): 1