C Tutorial/math.h/nan
nan
Item Value Header file math.h Declaratin float nanf(const char *content);double nan(const char *content);long double nanl(const char *content); Return returns a value that is not a number and that contains the string pointed to by content.
#include <math.h>
#include <stdio.h>
int main(void)
{
double f;
f = nan("2.0");
printf("%f " , f);
}