1LOG2(3)                    Linux Programmer's Manual                   LOG2(3)
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NAME

6       log2, log2f, log2l - base-2 logarithmic function
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SYNOPSIS

9       #include <math.h>
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11       double log2(double x);
12       float log2f(float x);
13       long double log2l(long double x);
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15       Link with -lm.
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17   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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19       log2(), log2f(), log2l():
20           _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
21           _POSIX_C_SOURCE >= 200112L;
22           or cc -std=c99
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DESCRIPTION

25       The log2() function returns the base 2 logarithm of x.
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RETURN VALUE

28       On success, these functions return the base 2 logarithm of x.
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30       For special cases, including where x is 0, 1,  negative,  infinity,  or
31       NaN, see log(3).
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ERRORS

34       See  math_error(7) for information on how to determine whether an error
35       has occurred when calling these functions.
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37       For a discussion of the errors that can occur for these functions,  see
38       log(3).
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VERSIONS

41       These functions first appeared in glibc in version 2.1.
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CONFORMING TO

44       C99, POSIX.1-2001.  The variant returning double also conforms to SVr4,
45       4.3BSD.
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SEE ALSO

48       cbrt(3), clog2(3), log(3), log10(3), sqrt(3)
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COLOPHON

51       This page is part of release 3.53 of the Linux  man-pages  project.   A
52       description  of  the project, and information about reporting bugs, can
53       be found at http://www.kernel.org/doc/man-pages/.
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57                                  2010-09-12                           LOG2(3)
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