gamma(3) — Linux manual page

gamma(3)                Library Functions Manual                gamma(3)

NAME

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

LIBRARY

       Math library (libm, -lm)

SYNOPSIS

       #include <math.h>

       [[deprecated]] double gamma(double x);
       [[deprecated]] float gammaf(float x);
       [[deprecated]] long double gammal(long double x);

   Feature Test Macro Requirements for glibc (see
   feature_test_macros(7)):

       gamma():
           _XOPEN_SOURCE
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

       gammaf(), gammal():
           _XOPEN_SOURCE >= 600 || (_XOPEN_SOURCE && _ISOC99_SOURCE)
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* glibc <= 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
       computes 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).
       ┌──────────────────────┬───────────────┬────────────────────────┐
       │ Interface            │ Attribute     │ Value                  │
       ├──────────────────────┼───────────────┼────────────────────────┤
       │ gamma(), gammaf(),   │ Thread safety │ MT-Unsafe race:signgam │
       │ gammal()             │               │                        │
       └──────────────────────┴───────────────┴────────────────────────┘

STANDARDS

       None.

HISTORY

       SVID 2.

       Because of historical variations in behavior across systems, this
       function is not specified in any recent standard.

       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)

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Linux man-pages 6.9.1          2024-05-02                       gamma(3)

Pages that refer to this page: tgamma(3)

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