получить целочисленную экспоненту значения с плавающей запятой (get integer exponent of a floating-point value)
Имя (Name)
ilogb, ilogbf, ilogbl - get integer exponent of a floating-point
value
Синопсис (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():
_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_SOURCE
Описание (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.
Возвращаемое значение (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.
Ошибки (Error)
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, and errno is set to EDOM (but see BUGS).
Domain error: x is an infinity
An invalid floating-point exception (FE_INVALID) is
raised, and errno is set to EDOM (but see BUGS).
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│ilogb(), ilogbf(), ilogbl() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
Стандарты (Conforming to)
C99, POSIX.1-2001, POSIX.1-2008.
Ошибки (баги) (Bugs)
Before version 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 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 to be set or raise a floating-point exception.
Смотри также (See also)
log(3), logb(3), significand(3)
