log2l - base-2 logarithmic function

NAME  LIBRARY  SYNOPSIS  DESCRIPTION  RETURN VALUE  ERRORS  ATTRIBUTES  STANDARDS  HISTORY  SEE ALSO 

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NAME

log2, log2f, log2l − base-2 logarithmic function

LIBRARY

Math library (libm, −lm)

SYNOPSIS

#include <math.h>

double log2(double x);
float log2f(float x);
long double log2l(long double x);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

log2(), log2f(), log2l():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

DESCRIPTION

These functions return the base 2 logarithm of x.

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).

ERRORS

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).

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

STANDARDS

C11, POSIX.1-2008.

HISTORY

glibc 2.1. C99, POSIX.1-2001.

The variant returning double also conforms to SVr4, 4.3BSD.

SEE ALSO

cbrt(3), clog2(3), log(3), log10(3), sqrt(3)

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