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**NAME**

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

**SYNOPSIS**

#include<math.h>doublegamma(doublex);floatgammaf(floatx);longdoublegammal(longdoublex);Link with-lm. Feature Test Macro Requirements for glibc (seefeature_test_macros(7)):gamma(): _XOPEN_SOURCE || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCEgammaf(),gammal(): _XOPEN_SOURCE >= 600 || (_XOPEN_SOURCE && _ISOC99_SOURCE) || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

**DESCRIPTION**

These functions are deprecated: instead, use either thetgamma(3) or thelgamma(3) functions, as appropriate. For the definition of the Gamma function, seetgamma(3).*BSDversionThe libm in 4.4BSD and some versions of FreeBSD had agamma() function that computes the Gamma function, as one would expect.glibcversionGlibc has agamma() function that is equivalent tolgamma(3) and computes the natural logarithm of the Gamma function.

**RETURN** **VALUE**

Seelgamma(3).

**ERRORS**

Seelgamma(3).

**ATTRIBUTES**

For an explanation of the terms used in this section, seeattributes(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**

History4.2BSD had agamma() that computed ln(|Gamma(|x|)|), leaving the sign of Gamma(|x|) in the external integersigngam. In 4.3BSD the name was changed tolgamma(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, wheregamma() computes the Gamma function (with no effect onsigngam). However, this came too late, and we now havetgamma(3), the "true gamma" function.

**SEE** **ALSO**

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

**COLOPHON**

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