ilogb, ilogbf---get exponent of floating point number

#include <math.h>
int ilogb(double val);
int ilogbf(float val);

All non zero, normal numbers can be described as m * 2**p. ilogb and ilogbf examine the argument val, and return p. The functions frexp and frexpf are similar to ilogb and ilogbf, but also return m.

Returns

ilogb and ilogbf return the power of two used to form the floating point argument. If val is 0, they return - INT_MAX (INT_MAX is defined in limits.h). If val is infinite, or NaN, they return INT_MAX.

Portability
Neither ilogb nor ilogbf is required by ANSI C or by the System V Interface Definition (Issue 2).