NAME

log2, log2f, log2l - base-2 logarithmic function

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(): _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99

DESCRIPTION

The log2() function returns the base 2 logarithm of x.

ERRORS

The log2() function can return the following error:

EDOM

The argument x is negative.

ERANGE

The argument x is zero. The log of zero is not defined (minus infinity).

CONFORMING TO

SVr4, 4.3BSD, C89. The float and long double variants are C99 requirements.

SEE ALSO

cbrt(3), clog2(3), sqrt(3)