LOG2(3) Linux Programmer's Manual LOG2(3)

NAME
       log2, log2f, log2l - base-2 logarithmic function

SYNOPSIS
       #include 

       double log2(double x);
       float log2f(float x);
       long double log2l(long double x);

       Link with -lm.

   Feature Test Macro Requirements for glibc (see featuretestmacros(7)):

       log2(), log2f(), log2l():
           XOPENSOURCE >= 600 || ISOC99SOURCE ||
           POSIXCSOURCE >= 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  matherror(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 3.53 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)