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 || _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99

DESCRIPTION

       The log2() function returns 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).

VERSIONS

       These functions first appeared in glibc in version 2.1.

CONFORMING TO

       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)

COLOPHON

       This page is part of release 3.54 of the Linux man-pages project.  A  description  of  the
       project,     and    information    about    reporting    bugs,    can    be    found    at
       http://www.kernel.org/doc/man-pages/.

                                            2010-09-12                                    LOG2(3)