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



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

SYNOPSIS
       #include <&lt;math.h>&gt;

       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; or
       cc -std=c99

DESCRIPTION
       The log2() function returns the base 2 logarithm of x.

ERRORS
       The log2() function can return the following error:

       EDOM   The argument x is negative.

       ERANGE The argument x is zero.  The log of zero is not  defined  (minus
              infinity).

CONFORMING TO
       SVr4, 4.3BSD, C89.  The float and long double variants are C99 require-
       ments.

SEE ALSO
       cbrt(3), clog2(3), sqrt(3)

COLOPHON
       This page is part of release 3.05 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/.



                                  2007-07-26                           LOG2(3)