LOG2
LOG2
Section: Linux Programmer's Manual (3) Updated: 2010-09-12 Local index
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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 || _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 3.27 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/.

Index
NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
VERSIONS
CONFORMING TO
SEE ALSO
COLOPHON
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Time: 21:49:36 GMT, April 16, 2011