логарифмическая функция по основанию 2 (base-2 logarithmic function)
Имя (Name)
log2, log2f, log2l - base-2 logarithmic function
Синопсис (Synopsis)
#include <math.h>
double log2(double x);
float log2f(float x);
long double log2l(long double x);
Link with -lm.
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
log2(), log2f(), log2l():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
Описание (Description)
These functions return the base 2 logarithm of x.
Возвращаемое значение (Return value)
On success, these functions return the base 2 logarithm of x.
For special cases, including where x is 0, 1, negative, infinity,
or NaN, see log(3).
Ошибки (Error)
See math_error(7) for information on how to determine whether an
error has occurred when calling these functions.
For a discussion of the errors that can occur for these
functions, see log(3).
Версии (Versions)
These functions first appeared in glibc in version 2.1.
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│log2(), log2f(), log2l() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
Стандарты (Conforming to)
C99, POSIX.1-2001, POSIX.1-2008.
The variant returning double also conforms to SVr4, 4.3BSD.
Смотри также (See also)
cbrt(3), clog2(3), log(3), log10(3), sqrt(3)
