log2, log2f, log2l - base-2 logarithmic function
#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
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).
These functions first appeared in glibc in version 2.1.
For an explanation of the terms used in this section, see
attributes(7).
| Interface |
Attribute |
Value |
| log2 (), log2f (), log2l () |
Thread safety |
MT-Safe |
C99, POSIX.1-2001, POSIX.1-2008.
The variant returning
double also conforms to SVr4, 4.3BSD.
cbrt(3),
clog2(3),
log(3),
log10(3),
sqrt(3)