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GAMMA(3) Linux Programmer's Manual GAMMA(3)
gamma, gammaf, gammal - (logarithm of the) gamma function
#include <math.h>
double gamma(double x);
float gammaf(float x);
long double gammal(long double x);
Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
gamma():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE
gammaf(), gammal():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600
These functions are deprecated: instead, use either the tgamma(3) or the
lgamma(3) functions, as appropriate.
For the definition of the Gamma function, see tgamma(3).
The libm in 4.4BSD and some versions of FreeBSD had a gamma() function that
computes the Gamma function, as one would expect.
Glibc has a gamma() function that is equivalent to lgamma(3) and computes the
natural logarithm of the Gamma function.
See lgamma(3).
See lgamma(3).
Because of historical variations in behavior across systems, this function is
not specified in any standard.
4.2BSD had a gamma() that computed ln(|Gamma(|x|)|), leaving the sign of
Gamma(|x|) in the external integer signgam. In 4.3BSD the name was changed to
lgamma(3), and the man page promises
"At some time in the future the name gamma will be rehabilitated and used
for the Gamma function"
This did indeed happen in 4.4BSD, where gamma() computes the Gamma function
(with no effect on signgam). However, this came too late, and we now have
tgamma(3), the "true gamma" function.
lgamma(3), signgam(3), tgamma(3)
This page is part of release 3.32 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/.
GNU 2008-08-05 GAMMA(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface