1GAMMA(3)                   Linux Programmer's Manual                  GAMMA(3)
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4

NAME

6       gamma, gammaf, gammal - (logarithm of the) gamma function
7

SYNOPSIS

9       #include <math.h>
10
11       double gamma(double x);
12       float gammaf(float x);
13       long double gammal(long double x);
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15       Link with -lm.
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17   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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19       gamma():
20           _XOPEN_SOURCE
21               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
22               || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
23       gammaf(), gammal():
24           _XOPEN_SOURCE >= 600 || (_XOPEN_SOURCE && _ISOC99_SOURCE)
25               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
26               || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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DESCRIPTION

29       These  functions  are  deprecated: instead, use either the tgamma(3) or
30       the lgamma(3) functions, as appropriate.
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32       For the definition of the Gamma function, see tgamma(3).
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34   *BSD version
35       The libm in 4.4BSD and some versions of FreeBSD had a gamma()  function
36       that computes the Gamma function, as one would expect.
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38   glibc version
39       Glibc  has  a gamma() function that is equivalent to lgamma(3) and com‐
40       putes the natural logarithm of the Gamma function.
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RETURN VALUE

43       See lgamma(3).
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ERRORS

46       See lgamma(3).
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ATTRIBUTES

49       For  an  explanation  of  the  terms  used   in   this   section,   see
50       attributes(7).
51
52       ┌────────────────────────────┬───────────────┬────────────────────────┐
53       │Interface                   │ Attribute     │ Value                  │
54       ├────────────────────────────┼───────────────┼────────────────────────┤
55       │gamma(), gammaf(), gammal() │ Thread safety │ MT-Unsafe race:signgam │
56       └────────────────────────────┴───────────────┴────────────────────────┘

CONFORMING TO

58       Because of historical variations in behavior across systems, this func‐
59       tion is not specified in any recent standard.   It  was  documented  in
60       SVID 2.
61

NOTES

63   History
64       4.2BSD  had  a gamma() that computed ln(|Gamma(|x|)|), leaving the sign
65       of Gamma(|x|) in the external integer signgam.  In 4.3BSD the name  was
66       changed to lgamma(3), and the man page promises
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68           "At  some  time  in the future the name gamma will be rehabilitated
69           and used for the Gamma function"
70
71       This did indeed happen in 4.4BSD,  where  gamma()  computes  the  Gamma
72       function (with no effect on signgam).  However, this came too late, and
73       we now have tgamma(3), the "true gamma" function.
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SEE ALSO

76       lgamma(3), signgam(3), tgamma(3)
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COLOPHON

79       This page is part of release 4.16 of the Linux  man-pages  project.   A
80       description  of  the project, information about reporting bugs, and the
81       latest    version    of    this    page,    can     be     found     at
82       https://www.kernel.org/doc/man-pages/.
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86GNU                               2017-09-15                          GAMMA(3)
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