NAME
gamma, gammaf, gammal - (logarithm of the) gamma function
SYNOPSIS
#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():
_XOPEN_SOURCE
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE ||
_SVID_SOURCE
gammaf(), gammal():
_XOPEN_SOURCE >= 600 ||
(_XOPEN_SOURCE && _ISOC99_SOURCE)
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE ||
_SVID_SOURCE
DESCRIPTION
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).
*BSD
version
The libm in 4.4BSD and some versions of FreeBSD had a
gamma() function that computes the Gamma function, as
one would expect.
glibc
version
Glibc has a gamma() function that is equivalent to
lgamma(3) and computes the natural logarithm of the
Gamma function.
RETURN VALUE
See lgamma(3).
ERRORS
See lgamma(3).
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
CONFORMING TO
Because of historical variations in behavior across systems, this function is not specified in any recent standard. It was documented in SVID 2.
NOTES
History
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.
SEE ALSO
lgamma(3), signgam(3), tgamma(3)
COLOPHON
This page is part of release 5.09 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.