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   ilogbf    ( 3 )

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)