1 .\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
3 .\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
4 .\" Distributed under GPL
7 .\" Modified 2003-11-18, aeb: historical remarks
9 .TH GAMMA 3 2017-09-15 "GNU" "Linux Programmer's Manual"
11 gamma, gammaf, gammal \- (logarithm of the) gamma function
15 .BI "double gamma(double " x ");"
17 .BI "float gammaf(float " x ");"
19 .BI "long double gammal(long double " x ");"
24 Feature Test Macro Requirements for glibc (see
25 .BR feature_test_macros (7)):
32 || /* Since glibc 2.19: */ _DEFAULT_SOURCE
33 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
38 _XOPEN_SOURCE >= 600 || (_XOPEN_SOURCE && _ISOC99_SOURCE)
39 || /* Since glibc 2.19: */ _DEFAULT_SOURCE
40 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
44 These functions are deprecated: instead, use either the
48 functions, as appropriate.
50 For the definition of the Gamma function, see
53 The libm in 4.4BSD and some versions of FreeBSD had a
55 function that computes the Gamma function, as one would expect.
59 function that is equivalent to
61 and computes the natural logarithm of the Gamma function.
69 For an explanation of the terms used in this section, see
75 Interface Attribute Value
80 T} Thread safety MT-Unsafe race:signgam
83 Because of historical variations in behavior across systems,
84 this function is not specified in any recent standard.
85 It was documented in SVID 2.
91 .RI ln(|Gamma(| x |)|),
94 in the external integer
96 In 4.3BSD the name was changed to
98 and the man page promises
101 "At some time in the future the name gamma will be rehabilitated
102 and used for the Gamma function"
105 This did indeed happen in 4.4BSD, where
107 computes the Gamma function (with no effect on
109 However, this came too late, and we now have
111 the "true gamma" function.
112 .\" The FreeBSD man page says about gamma() that it is like lgamma()
113 .\" except that is does not set signgam.
114 .\" Also, that 4.4BSD has a gamma() that computes the true gamma function.