
GAMMA(3) Linux Programmer's Manual GAMMA(3)
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():
_BSD_SOURCE  _SVID_SOURCE  _XOPEN_SOURCE
gammaf(), gammal():
_BSD_SOURCE  _SVID_SOURCE  _XOPEN_SOURCE >= 600
DESCRIPTION
These functions are deprecated: instead, use either the tgamma(3) or the lgamma(3) func
tions, 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 log
arithm of the Gamma function.
RETURN VALUE
See lgamma(3).
ERRORS
See lgamma(3).
CONFORMING TO
Because of historical variations in behavior across systems, this function is not speci
fied in any standard.
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 3.55 of the Linux manpages project. A description of the
project, and information about reporting bugs, can be found at
http://www.kernel.org/doc/manpages/.
GNU 20080805 GAMMA(3) 
