NAME

ilogb, ilogbf, ilogbl - return an unbiased exponent

SYNOPSIS

c99 [ flag... ] file... -lm [ library... ]
#include <math.h>
int ilogb(double x);

int ilogbf(float x);

int ilogbl(long double x);

cc [ flag... ] file... -lm [ library... ]
#include <math.h>
int ilogb(double x);

int ilogbf(float x);

int ilogbl(long double x);

DESCRIPTION

These functions return the exponent part of their argument x. Formally, the return value is the integral part of log(r)| x | as a signed integral value, for non-zero x, where r is the radix of the machine's floating point arithmetic, which is the value of FLT_RADIX defined in <float.h>.

RETURN VALUES

Upon successful completion, these functions return the exponent part of x as a signed integer value. They are equivalent to calling the corresponding logb(3M) function and casting the returned value to type int.

If x is 0, the value FP_ILOGB0 is returned. For SUSv3-conforming applications compiled with the c99 compiler driver (see standards(7)), a domain error occurs.

If x is ±Inf, the value INT_MAX is returned. For SUSv3-conforming applications compiled with the c99 compiler driver, a domain error occurs.

If x is NaN, the value FP_ILOGBNAN is returned. For SUSv3-conforming applications compiled with the c99 compiler driver, a domain error occurs.

ERRORS

These functions will fail if:

Domain Error

The x argument is zero, NaN, or ±Inf.

If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception is raised.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE	ATTRIBUTE VALUE
Interface Stability	Standard
MT-Level	MT-Safe