gammal(3) — Linux manual page


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

NAME         top

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

SYNOPSIS         top

       #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)):

               || /* 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         top

       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         top

       See lgamma(3).

ERRORS         top

       See lgamma(3).

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface                   Attribute     Value                  │
       │gamma(), gammaf(), gammal() │ Thread safety │ MT-Unsafe race:signgam │

CONFORMING TO         top

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

NOTES         top

       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         top

       lgamma(3), signgam(3), tgamma(3)

COLOPHON         top

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GNU                              2017-09-15                         GAMMA(3)