gamma(3)

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

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

9       #include <math.h>
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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(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE
20       gammaf(), gammal(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600
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DESCRIPTION

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

37       See lgamma(3).
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ERRORS

40       See lgamma(3).
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CONFORMING TO

43       Because of historical variations in behavior across systems, this func‐
44       tion is not specified in any standard.
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NOTES

47   History
48       4.2BSD  had  a gamma() that computed ln(|Gamma(|x|)|), leaving the sign
49       of Gamma(|x|) in the external integer signgam.  In 4.3BSD the name  was
50       changed to lgamma(3), and the man page promises
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52           "At  some  time  in the future the name gamma will be rehabilitated
53           and used for the Gamma function"
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55       This did indeed happen in 4.4BSD,  where  gamma()  computes  the  Gamma
56       function (with no effect on signgam).  However, this came too late, and
57       we now have tgamma(3), the "true gamma" function.
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COLOPHON

63       This page is part of release 3.22 of the Linux  man-pages  project.   A
64       description  of  the project, and information about reporting bugs, can
65       be found at http://www.kernel.org/doc/man-pages/.
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69GNU                               2008-08-05                          GAMMA(3)