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():
           _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) func‐
       tions, 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 log‐
       arithm 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  speci‐
       fied 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
       This page is part of release 3.74 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 http://www.kernel.org/doc/man-pages/.



GNU                                         2008-08-05                                   GAMMA(3)