'\" t .\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de) .\" .\" SPDX-License-Identifier: GPL-1.0-or-later .\" .\" Modified 2003-11-18, aeb: historical remarks .\" .TH gamma 3 2024-05-02 "Linux man-pages 6.8" .SH NAME gamma, gammaf, gammal \- (logarithm of the) gamma function .SH LIBRARY Math library .RI ( libm ", " \-lm ) .SH SYNOPSIS .nf .B #include .P .BI "[[deprecated]] double gamma(double " x ");" .BI "[[deprecated]] float gammaf(float " x ");" .BI "[[deprecated]] long double gammal(long double " x ");" .fi .P .RS -4 Feature Test Macro Requirements for glibc (see .BR feature_test_macros (7)): .RE .P .BR gamma (): .nf _XOPEN_SOURCE || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE .fi .P .BR gammaf (), .BR gammal (): .nf _XOPEN_SOURCE >= 600 || (_XOPEN_SOURCE && _ISOC99_SOURCE) || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE .fi .SH DESCRIPTION These functions are deprecated: instead, use either the .BR tgamma (3) or the .BR lgamma (3) functions, as appropriate. .P For the definition of the Gamma function, see .BR tgamma (3). .SS *BSD version The libm in 4.4BSD and some versions of FreeBSD had a .BR gamma () function that computes the Gamma function, as one would expect. .SS glibc version glibc has a .BR gamma () function that is equivalent to .BR lgamma (3) and computes the natural logarithm of the Gamma function. .SH RETURN VALUE See .BR lgamma (3). .SH ERRORS See .BR lgamma (3). .SH ATTRIBUTES For an explanation of the terms used in this section, see .BR attributes (7). .TS allbox; lbx lb lb l l l. Interface Attribute Value T{ .na .nh .BR gamma (), .BR gammaf (), .BR gammal () T} Thread safety MT-Unsafe race:signgam .TE .SH STANDARDS None. .SH HISTORY SVID 2. .P Because of historical variations in behavior across systems, this function is not specified in any recent standard. .P 4.2BSD had a .BR gamma () that computed .RI ln(|Gamma(| x |)|), leaving the sign of .RI Gamma(| x |) in the external integer .IR signgam . In 4.3BSD the name was changed to .BR lgamma (3), and the man page promises .P .in +4n "At some time in the future the name gamma will be rehabilitated and used for the Gamma function" .in .P This did indeed happen in 4.4BSD, where .BR gamma () computes the Gamma function (with no effect on .IR signgam ). However, this came too late, and we now have .BR tgamma (3), the "true gamma" function. .\" The FreeBSD man page says about gamma() that it is like lgamma() .\" except that is does not set signgam. .\" Also, that 4.4BSD has a gamma() that computes the true gamma function. .SH SEE ALSO .BR lgamma (3), .BR signgam (3), .BR tgamma (3)