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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       information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.