gamma(3) - Linux manual page (original) (raw)

gamma(3) Library Functions Manual gamma(3)

NAME top

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

LIBRARY top

   Math library (_libm_, _-lm_)

SYNOPSIS top

   **#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 top

   These functions are deprecated: instead, use either the [tgamma(3)](../man3/tgamma.3.html)
   or the [lgamma(3)](../man3/lgamma.3.html) functions, as appropriate.

   For the definition of the Gamma function, see [tgamma(3)](../man3/tgamma.3.html).

*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)](../man3/lgamma.3.html).

ERRORS top

   See [lgamma(3)](../man3/lgamma.3.html).

ATTRIBUTES top

   For an explanation of the terms used in this section, see
   [attributes(7)](../man7/attributes.7.html).
   ┌───────────────────────┬───────────────┬────────────────────────┐
   │ **Interface** │ **Attribute** │ **Value** │
   ├───────────────────────┼───────────────┼────────────────────────┤
   │ **gamma**(), **gammaf**(),    │ Thread safety │ MT-Unsafe race:signgam │
   │ **gammal**()              │               │                        │
   └───────────────────────┴───────────────┴────────────────────────┘

STANDARDS top

   None.

HISTORY top

   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)](../man3/lgamma.3.html), 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)](../man3/tgamma.3.html), the "true gamma" function.

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Linux man-pages 6.10 2024-07-23 gamma(3)

Pages that refer to this page:tgamma(3)