## table of contents

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

# NAME¶

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

# SYNOPSIS¶

#include <math.h>

double gamma(doublex);float gammaf(floatx);long double gammal(long doublex);

Link with *-lm*.

**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 (), gammal () | Thread safety | MT-Unsafe race:signgam |

# CONFORMING TO¶

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

# 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¶

# COLOPHON¶

This page is part of release 5.13 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
https://www.kernel.org/doc/man-pages/.

2021-03-22 | GNU |