| ILOGB(3) | Library Functions Manual | ILOGB(3) | 
ilogb, ilogbf,
  ilogbl —
#include <math.h>
int
  
  ilogb(double
    x);
int
  
  ilogbf(float
    x);
int
  
  ilogbl(long
    double x);
ilogb(), ilogbf(), and
  ilogbl() functions return the exponent of the non-zero
  real floating-point number x as a signed integer value.
  Formally the return value is the integral part of
where r is the radix of the machine's
    floating-point arithmetic defined by the FLT_RADIX
    constant in <float.h>.
The following special cases may occur:
FP_ILOGB0 is returned and a domain error
    occurs.INT_MAX is returned.FP_ILOGBNAN is returned.| August 22, 2016 | NetBSD 10.0 |