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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(): _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L; or cc -std=c99
The log2() function returns 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.
C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD.
This page is part of release 3.35 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://man7.org/linux/man- pages/. 2010-09-12 LOG2(3)