ILOGB(3)

NAME
ilogb, ilogbf, ilogbl - an unbiased exponent

LIBRARY
libm

SYNOPSIS
#include <math.h>
int
ilogb(double x);
int
ilogbf(float x);
int
ilogbl(long double x);

DESCRIPTION
The 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

log_r | x |,

where r is the radix of the machine's floating-point arithmetic defined by the FLT_RADIX constant in <float.h>.

RETURN VALUES
As described above, upon successful completion, the functions return the exponent. Functionally this is the same as calling the corresponding logb(3) function and casting the return value to int.

The following special cases may occur:

1.  If x is zero, the value of FP_ILOGB0 is returned and a domain error occurs.

2.  If x is infinite, a domain error occurs and the value of INT_MAX is returned.

3.  If x is , a domain error is raised and the value of FP_ILOGBNAN is returned.

4.  If the correct value is outside the range of the return type, a domain error occurs but an unspecified value is returned.

SEE ALSO
ilog2(3), logb(3), math(3)

STANDARDS
The described functions conform to isoC-99.