1GAMMA(3)                   Linux Programmer's Manual                  GAMMA(3)
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3
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);
14
15       Link with -lm.
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17   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
18
19       gamma():
20           _XOPEN_SOURCE
21               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
22               || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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24       gammaf(), gammal():
25           _XOPEN_SOURCE >= 600 || (_XOPEN_SOURCE && _ISOC99_SOURCE)
26               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
27               || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
28

DESCRIPTION

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

44       See lgamma(3).
45

ERRORS

47       See lgamma(3).
48

ATTRIBUTES

50       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
51       tributes(7).
52
53       ┌─────────────────────────────┬───────────────┬────────────────────────┐
54       │Interface                    │ Attribute     │ Value                  │
55       ├─────────────────────────────┼───────────────┼────────────────────────┤
56       │gamma(), gammaf(), gammal()  │ Thread safety │ MT-Unsafe race:signgam │
57       └─────────────────────────────┴───────────────┴────────────────────────┘
58

CONFORMING TO

60       Because of historical variations in behavior across systems, this func‐
61       tion is not specified in any recent standard.   It  was  documented  in
62       SVID 2.
63

NOTES

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

78       lgamma(3), signgam(3), tgamma(3)
79

COLOPHON

81       This page is part of release 5.13 of the Linux  man-pages  project.   A
82       description  of  the project, information about reporting bugs, and the
83       latest    version    of    this    page,    can     be     found     at
84       https://www.kernel.org/doc/man-pages/.
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88GNU                               2021-03-22                          GAMMA(3)
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