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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; 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, C89.

SEE ALSO

       cbrt(3), clog2(3), sqrt(3)

COLOPHON

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                                  2008-08-11