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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) functions, 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 logarithm 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 specified 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

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