ILOGB
Section: Linux Programmer's Manual (3)
Updated: 2009-02-04
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NAME
ilogb, ilogbf, ilogbl - get integer exponent of a floating-point value
SYNOPSIS
#include <math.h>
int ilogb(double x);
int ilogbf(float x);
int ilogbl(long double x);
Link with -lm.
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
ilogb():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE; or
cc -std=c99
ilogbf(),
ilogbl():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or
cc -std=c99
DESCRIPTION
These functions return the exponent part of their argument
as a signed integer.
When no error occurs, these functions
are equivalent to the corresponding
logb(3)
functions, cast to
int.
RETURN VALUE
On success, these functions return the exponent of
x,
as a signed integer.
If
x
is zero, then a domain error occurs, and the functions return
FP_ILOGB0.
If
x
is a NaN, then a domain error occurs, and the functions return
FP_ILOGBNAN.
If
x
is negative infinity or positive infinity, then
a domain error occurs, and the functions return
INT_MAX.
ERRORS
See
math_error(7)
for information on how to determine whether an error has occurred
when calling these functions.
The following errors can occur:
- Domain error: x is 0 or a NaN
-
An invalid floating-point exception
(FE_INVALID)
is raised.
-
These functions do not set
errno
for this case.
- Domain error: x is an infinity
-
-
These functions do not set
errno
or raise an exception for this case.
CONFORMING TO
C99, POSIX.1-2001.
SEE ALSO
log(3),
logb(3),
significand(3)
COLOPHON
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