C/math.h/ilogb
ilogb: returns the exponent of num
//Declaration: int ilogbf(float num);
int ilogb(double num);
int ilogbl(long double num);
#include <math.h>
#include <stdio.h>
int main(void)
{
int e;
e = ilogbl(4);
printf("%d", e);
}
/*2*/