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():
_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
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).
For an explanation of the terms used in this section, see
attributes(7).
| Interface |
Attribute |
Value |
| gamma (), gammaf (), gammal () |
Thread safety |
MT-Unsafe race:signgam |
Because of historical variations in behavior across systems, this function is
not specified in any recent standard. It was documented in SVID 2.
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)