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gamma(3)


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():
       _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

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).

ATTRIBUTES

   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

CONFORMING TO

   Because  of  historical  variations  in  behavior  across systems, this
   function is not specified in any recent standard.  It was documented in
   SVID 2.

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

   This page is part of release 4.09 of the Linux  man-pages  project.   A
   description  of  the project, information about reporting bugs, and the
   latest    version    of    this    page,    can     be     found     at
   https://www.kernel.org/doc/man-pages/.



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