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1 | .\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de) | |
2 | .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk | |
3 | .\" <mtk.manpages@gmail.com> | |
4 | .\" | |
5 | .\" %%%LICENSE_START(GPL_NOVERSION_ONELINE) | |
6 | .\" Distributed under GPL | |
7 | .\" %%%LICENSE_END | |
8 | .\" | |
9 | .\" based on glibc infopages | |
10 | .\" | |
11 | .TH LGAMMA 3 2017-09-15 "" "Linux Programmer's Manual" | |
12 | .SH NAME | |
13 | lgamma, lgammaf, lgammal, lgamma_r, lgammaf_r, lgammal_r, signgam \- | |
14 | log gamma function | |
15 | .SH SYNOPSIS | |
16 | .nf | |
17 | .B #include <math.h> | |
18 | .PP | |
19 | .BI "double lgamma(double " x ); | |
20 | .BI "float lgammaf(float " x ); | |
21 | .BI "long double lgammal(long double " x ); | |
22 | .PP | |
23 | .BI "double lgamma_r(double " x ", int *" signp ); | |
24 | .BI "float lgammaf_r(float " x ", int *" signp ); | |
25 | .BI "long double lgammal_r(long double " x ", int *" signp ); | |
26 | .PP | |
27 | .BI "extern int " signgam ; | |
28 | .fi | |
29 | .PP | |
30 | Link with \fI\-lm\fP. | |
31 | .PP | |
32 | .in -4n | |
33 | Feature Test Macro Requirements for glibc (see | |
34 | .BR feature_test_macros (7)): | |
35 | .in | |
36 | .PP | |
37 | .ad l | |
38 | .BR lgamma (): | |
39 | .RS 4 | |
40 | _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L || _XOPEN_SOURCE | |
41 | || /* Since glibc 2.19: */ _DEFAULT_SOURCE | |
42 | || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE | |
43 | .RE | |
44 | .br | |
45 | .BR lgammaf (), | |
46 | .BR lgammal (): | |
47 | .RS 4 | |
48 | _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L | |
49 | || /* Since glibc 2.19: */ _DEFAULT_SOURCE | |
50 | || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE | |
51 | .RE | |
52 | .BR lgamma_r (), | |
53 | .BR lgammaf_r (), | |
54 | .BR lgammal_r (): | |
55 | .RS 4 | |
56 | /* Since glibc 2.19: */ _DEFAULT_SOURCE | |
57 | || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE | |
58 | .RE | |
59 | .IR signgam : | |
60 | .RS 4 | |
61 | _XOPEN_SOURCE | |
62 | || /* Since glibc 2.19: */ _DEFAULT_SOURCE | |
63 | || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE | |
64 | .RE | |
65 | .ad b | |
66 | .SH DESCRIPTION | |
67 | For the definition of the Gamma function, see | |
68 | .BR tgamma (3). | |
69 | .PP | |
70 | The | |
71 | .BR lgamma (), | |
72 | .BR lgammaf (), | |
73 | and | |
74 | .BR lgammal () | |
75 | functions return the natural logarithm of | |
76 | the absolute value of the Gamma function. | |
77 | The sign of the Gamma function is returned in the | |
78 | external integer | |
79 | .I signgam | |
80 | declared in | |
81 | .IR <math.h> . | |
82 | It is 1 when the Gamma function is positive or zero, \-1 | |
83 | when it is negative. | |
84 | .PP | |
85 | Since using a constant location | |
86 | .I signgam | |
87 | is not thread-safe, the functions | |
88 | .BR lgamma_r (), | |
89 | .BR lgammaf_r (), | |
90 | and | |
91 | .BR lgammal_r () | |
92 | have been introduced; they return the sign via the argument | |
93 | .IR signp . | |
94 | .SH RETURN VALUE | |
95 | On success, these functions return the natural logarithm of Gamma(x). | |
96 | .PP | |
97 | If | |
98 | .I x | |
99 | is a NaN, a NaN is returned. | |
100 | .PP | |
101 | If | |
102 | .I x | |
103 | is 1 or 2, +0 is returned. | |
104 | .PP | |
105 | If | |
106 | .I x | |
107 | is positive infinity or negative infinity, | |
108 | positive infinity is returned. | |
109 | .PP | |
110 | If | |
111 | .I x | |
112 | is a nonpositive integer, | |
113 | a pole error occurs, | |
114 | and the functions return | |
115 | .RB + HUGE_VAL , | |
116 | .RB + HUGE_VALF , | |
117 | or | |
118 | .RB + HUGE_VALL , | |
119 | respectively. | |
120 | .PP | |
121 | If the result overflows, | |
122 | a range error occurs, | |
123 | .\" e.g., lgamma(DBL_MAX) | |
124 | and the functions return | |
125 | .BR HUGE_VAL , | |
126 | .BR HUGE_VALF , | |
127 | or | |
128 | .BR HUGE_VALL , | |
129 | respectively, with the correct mathematical sign. | |
130 | .SH ERRORS | |
131 | See | |
132 | .BR math_error (7) | |
133 | for information on how to determine whether an error has occurred | |
134 | when calling these functions. | |
135 | .PP | |
136 | The following errors can occur: | |
137 | .TP | |
138 | Pole error: \fIx\fP is a nonpositive integer | |
139 | .I errno | |
140 | is set to | |
141 | .BR ERANGE | |
142 | (but see BUGS). | |
143 | A divide-by-zero floating-point exception | |
144 | .RB ( FE_DIVBYZERO ) | |
145 | is raised. | |
146 | .TP | |
147 | Range error: result overflow | |
148 | .I errno | |
149 | is set to | |
150 | .BR ERANGE . | |
151 | An overflow floating-point exception | |
152 | .RB ( FE_OVERFLOW ) | |
153 | is raised. | |
154 | .\" glibc (as at 2.8) also supports an inexact | |
155 | .\" exception for various cases. | |
156 | .SH CONFORMING TO | |
157 | The | |
158 | .BR lgamma () | |
159 | functions are specified in C99, POSIX.1-2001, and POSIX.1-2008. | |
160 | .I signgam | |
161 | is specified in POSIX.1-2001 and POSIX.1-2008, but not in C99. | |
162 | The | |
163 | .BR lgamma_r () | |
164 | functions are nonstandard, but present on several other systems. | |
165 | .SH BUGS | |
166 | In glibc 2.9 and earlier, | |
167 | .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6777 | |
168 | when a pole error occurs, | |
169 | .I errno | |
170 | is set to | |
171 | .BR EDOM ; | |
172 | instead of the POSIX-mandated | |
173 | .BR ERANGE . | |
174 | Since version 2.10, glibc does the right thing. | |
175 | .SH SEE ALSO | |
176 | .BR tgamma (3) |