log2, log2f, log2l − base-2 logarithmic function
Math library (libm, −lm)
#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
These functions return the base 2 logarithm of x.
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).
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).
For an explanation of the terms used in this section, see attributes(7). |
C11, POSIX.1-2008.
glibc 2.1. C99, POSIX.1-2001.
The variant returning double also conforms to SVr4, 4.3BSD.
cbrt(3), clog2(3), log(3), log10(3), sqrt(3)