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GAMMA(3)                   Linux Programmer's Manual                  GAMMA(3)



NAME
       gamma, gammaf, gammal - (logarithm of the) gamma function

SYNOPSIS
       #include <&lt;math.h>&gt;

       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(), gammaf(), gammal(): _BSD_SOURCE || _SVID_SOURCE ||
       _XOPEN_SOURCE

DESCRIPTION
       For the definition of the Gamma function, see tgamma(3).

   *BSD version
       4.4BSD and FreeBSD libm have 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.  (This is  for  com-
       patibility reasons only.  Don't use this function.)

CONFORMING TO
       4.2BSD.  Compatible with previous mistakes.

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 3.05 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.



GNU                               2007-07-26                          GAMMA(3)