ilogb(3M) Mathematical Library Functions ilogb(3M)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. For‐
mally, the return value is the integral part of logr| 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 corre‐
sponding logb(3M) function and casting the returned value to type int.
If x is 0, the value FP_ILOGB0 is returned. For SUSv3-conforming appli‐
cations compiled with the c99 compiler driver (see standards(5)), 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(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Standard │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │MT-Safe │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOfeclearexcept(3M), fetestexcept(3M), limits.h(3HEAD), logb(3M),
math.h(3HEAD), scalb(3M), attributes(5), standards(5)SunOS 5.10 12 Jul 2006 ilogb(3M)