GAMMA(3)                   Linux Programmer's Manual                  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 com-
       putes 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).

       allbox;  lbw27 lb lb l l l.  Interface Attribute Value T{ gamma(), gam-
       maf(), gammal() T}   Thread safety  MT-Unsafe race:signgam

CONFORMING TO
       Because of historical variations in behavior across systems, this func-
       tion  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 4.16 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/.



GNU                               2017-09-15                          GAMMA(3)