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fea681da | 1 | .\" Copyright 1995 Jim Van Zandt <jrv@vanzandt.mv.com> |
caba2e47 MK |
2 | .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk |
3 | .\" <mtk.manpages@gmail.com> | |
fea681da | 4 | .\" |
93015253 | 5 | .\" %%%LICENSE_START(VERBATIM) |
fea681da MK |
6 | .\" Permission is granted to make and distribute verbatim copies of this |
7 | .\" manual provided the copyright notice and this permission notice are | |
8 | .\" preserved on all copies. | |
9 | .\" | |
10 | .\" Permission is granted to copy and distribute modified versions of this | |
11 | .\" manual under the conditions for verbatim copying, provided that the | |
12 | .\" entire resulting derived work is distributed under the terms of a | |
13 | .\" permission notice identical to this one. | |
c13182ef | 14 | .\" |
fea681da MK |
15 | .\" Since the Linux kernel and libraries are constantly changing, this |
16 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
17 | .\" responsibility for errors or omissions, or for damages resulting from | |
18 | .\" the use of the information contained herein. The author(s) may not | |
19 | .\" have taken the same level of care in the production of this manual, | |
20 | .\" which is licensed free of charge, as they might when working | |
21 | .\" professionally. | |
c13182ef | 22 | .\" |
fea681da MK |
23 | .\" Formatted or processed versions of this manual, if unaccompanied by |
24 | .\" the source, must acknowledge the copyright and authors of this work. | |
4b72fb64 | 25 | .\" %%%LICENSE_END |
fea681da MK |
26 | .\" |
27 | .\" Modified 2002-07-27 by Walter Harms | |
28 | .\" (walter.harms@informatik.uni-oldenburg.de) | |
4b8c67d9 | 29 | .TH LOG1P 3 2017-09-15 "" "Linux Programmer's Manual" |
fea681da | 30 | .SH NAME |
9a2d673e | 31 | log1p, log1pf, log1pl \- logarithm of 1 plus argument |
fea681da MK |
32 | .SH SYNOPSIS |
33 | .nf | |
34 | .B #include <math.h> | |
68e4db0a | 35 | .PP |
fea681da | 36 | .BI "double log1p(double " x ); |
fea681da | 37 | .BI "float log1pf(float " x ); |
fea681da | 38 | .BI "long double log1pl(long double " x ); |
68e4db0a | 39 | .PP |
fea681da | 40 | .fi |
cc4615cc | 41 | Link with \fI\-lm\fP. |
68e4db0a | 42 | .PP |
cc4615cc MK |
43 | .in -4n |
44 | Feature Test Macro Requirements for glibc (see | |
45 | .BR feature_test_macros (7)): | |
46 | .in | |
68e4db0a | 47 | .PP |
cc4615cc | 48 | .ad l |
caba2e47 | 49 | .BR log1p (): |
1b5ffa62 | 50 | .RS 4 |
636ed4d5 MK |
51 | _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L |
52 | || _XOPEN_SOURCE\ >=\ 500 | |
cf7fa0a1 | 53 | .\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED |
636ed4d5 MK |
54 | || /* Since glibc 2.19: */ _DEFAULT_SOURCE |
55 | || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE | |
1b5ffa62 | 56 | .RE |
caba2e47 | 57 | .br |
cc4615cc MK |
58 | .BR log1pf (), |
59 | .BR log1pl (): | |
1b5ffa62 | 60 | .RS 4 |
636ed4d5 MK |
61 | _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L |
62 | || /* Since glibc 2.19: */ _DEFAULT_SOURCE | |
63 | || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE | |
1b5ffa62 | 64 | .RE |
cc4615cc | 65 | .ad b |
fea681da | 66 | .SH DESCRIPTION |
5600f73a | 67 | These functions return a value equivalent to |
207050fa | 68 | .PP |
2d986c92 | 69 | .nf |
2d986c92 | 70 | log (1 + \fIx\fP) |
2d986c92 | 71 | .fi |
207050fa | 72 | .PP |
5600f73a | 73 | The result is computed in a way |
022671eb MK |
74 | that is accurate even if the value of |
75 | .I x | |
76 | is near zero. | |
caba2e47 MK |
77 | .SH RETURN VALUE |
78 | On success, these functions return the natural logarithm of | |
79 | .IR "(1\ +\ x)" . | |
847e0d88 | 80 | .PP |
caba2e47 MK |
81 | If |
82 | .I x | |
83 | is a NaN, | |
84 | a NaN is returned. | |
847e0d88 | 85 | .PP |
caba2e47 MK |
86 | If |
87 | .I x | |
88 | is positive infinity, positive infinity is returned. | |
847e0d88 | 89 | .PP |
caba2e47 MK |
90 | If |
91 | .I x | |
efe294cb | 92 | is \-1, a pole error occurs, |
caba2e47 MK |
93 | and the functions return |
94 | .RB - HUGE_VAL , | |
95 | .RB - HUGE_VALF , | |
96 | or | |
97 | .RB - HUGE_VALL , | |
98 | respectively. | |
847e0d88 | 99 | .PP |
caba2e47 MK |
100 | If |
101 | .I x | |
102 | is less than \-1 (including negative infinity), | |
efe294cb | 103 | a domain error occurs, |
caba2e47 MK |
104 | and a NaN (not a number) is returned. |
105 | .\" POSIX.1 specifies a possible range error if x is subnormal | |
106 | .\" glibc 2.8 doesn't do this | |
107 | .SH ERRORS | |
108 | See | |
109 | .BR math_error (7) | |
110 | for information on how to determine whether an error has occurred | |
111 | when calling these functions. | |
112 | .PP | |
113 | The following errors can occur: | |
114 | .TP | |
115 | Domain error: \fIx\fP is less than \-1 | |
523e7e59 AH |
116 | .I errno |
117 | is set to | |
118 | .BR EDOM | |
119 | (but see BUGS). | |
caba2e47 MK |
120 | An invalid floating-point exception |
121 | .RB ( FE_INVALID ) | |
122 | is raised. | |
123 | .TP | |
124 | Pole error: \fIx\fP is \-1 | |
523e7e59 AH |
125 | .I errno |
126 | is set to | |
127 | .BR ERANGE | |
128 | (but see BUGS). | |
caba2e47 MK |
129 | A divide-by-zero floating-point exception |
130 | .RB ( FE_DIVBYZERO ) | |
131 | is raised. | |
d05cb848 | 132 | .SH ATTRIBUTES |
eb71cf70 MK |
133 | For an explanation of the terms used in this section, see |
134 | .BR attributes (7). | |
135 | .TS | |
136 | allbox; | |
137 | lbw27 lb lb | |
138 | l l l. | |
139 | Interface Attribute Value | |
140 | T{ | |
d05cb848 PH |
141 | .BR log1p (), |
142 | .BR log1pf (), | |
d05cb848 | 143 | .BR log1pl () |
eb71cf70 MK |
144 | T} Thread safety MT-Safe |
145 | .TE | |
47297adb | 146 | .SH CONFORMING TO |
9a74e018 | 147 | C99, POSIX.1-2001, POSIX.1-2008. |
caba2e47 | 148 | .\" BSD |
523e7e59 AH |
149 | .SH BUGS |
150 | Before version 2.22, the glibc implementation did not set | |
151 | .\" https://www.sourceware.org/bugzilla/show_bug.cgi?id=6792 | |
152 | .I errno | |
153 | to | |
154 | .B EDOM | |
155 | when a domain error occurred. | |
847e0d88 | 156 | .PP |
523e7e59 AH |
157 | Before version 2.22, the glibc implementation did not set |
158 | .\" https://www.sourceware.org/bugzilla/show_bug.cgi?id=6792 | |
159 | .I errno | |
160 | to | |
161 | .B ERANGE | |
162 | when a range error occurred. | |
47297adb | 163 | .SH SEE ALSO |
fea681da MK |
164 | .BR exp (3), |
165 | .BR expm1 (3), | |
166 | .BR log (3) |