ilogb(3) - Linux manual page (original) (raw)
ilogb(3) Library Functions Manual ilogb(3)
NAME top
ilogb, ilogbf, ilogbl - get integer exponent of a floating-point
valueLIBRARY top
Math library (_libm_, _-lm_)SYNOPSIS top
**#include <math.h>**
**int ilogb(double** _x_**);**
**int ilogbf(float** _x_**);**
**int ilogbl(long double** _x_**);**Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
**ilogb**():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| _XOPEN_SOURCE >= 500
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
**ilogbf**(), **ilogbl**():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCEDESCRIPTION top
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)](../man3/logb.3.html) functions, cast to _int_.RETURN VALUE top
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 top
See [math_error(7)](../man7/math%5Ferror.7.html) 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,
and _[errno](../man3/errno.3.html)_ is set to **EDOM** (but see BUGS).
Domain error: _x_ is an infinity
An invalid floating-point exception (**FE_INVALID**) is raised,
and _[errno](../man3/errno.3.html)_ is set to **EDOM** (but see BUGS).ATTRIBUTES top
For an explanation of the terms used in this section, see
[attributes(7)](../man7/attributes.7.html).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ **Interface** │ **Attribute** │ **Value** │
├──────────────────────────────────────┼───────────────┼─────────┤
│ **ilogb**(), **ilogbf**(), **ilogbl**() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘STANDARDS top
C11, POSIX.1-2008.HISTORY top
C99, POSIX.1-2001.BUGS top
Before glibc 2.16, the following bugs existed in the glibc
implementation of these functions:
• The domain error case where _x_ is 0 or a NaN did not cause _[errno](../man3/errno.3.html)_
to be set or (on some architectures) raise a floating-point
exception.
• The domain error case where _x_ is an infinity did not cause
_[errno](../man3/errno.3.html)_ to be set or raise a floating-point exception.SEE ALSO top
[log(3)](../man3/log.3.html), [logb(3)](../man3/logb.3.html), [significand(3)](../man3/significand.3.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-07-23 ilogb(3)
Pages that refer to this page:logb(3), significand(3)