]>
Commit | Line | Data |
---|---|---|
a1eaacb1 | 1 | '\" t |
fea681da | 2 | .\" Copyright 1995 Jim Van Zandt <jrv@vanzandt.mv.com> |
caba2e47 MK |
3 | .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk |
4 | .\" <mtk.manpages@gmail.com> | |
fea681da | 5 | .\" |
5fbde956 | 6 | .\" SPDX-License-Identifier: Linux-man-pages-copyleft |
fea681da MK |
7 | .\" |
8 | .\" Modified 2002-07-27 by Walter Harms | |
9 | .\" (walter.harms@informatik.uni-oldenburg.de) | |
a5ebdc8d | 10 | .TH log1p 3 (date) "Linux man-pages (unreleased)" |
fea681da | 11 | .SH NAME |
9a2d673e | 12 | log1p, log1pf, log1pl \- logarithm of 1 plus argument |
297a126f AC |
13 | .SH LIBRARY |
14 | Math library | |
8fc3b2cf | 15 | .RI ( libm ", " \-lm ) |
fea681da MK |
16 | .SH SYNOPSIS |
17 | .nf | |
18 | .B #include <math.h> | |
68e4db0a | 19 | .PP |
fea681da | 20 | .BI "double log1p(double " x ); |
fea681da | 21 | .BI "float log1pf(float " x ); |
fea681da | 22 | .BI "long double log1pl(long double " x ); |
68e4db0a | 23 | .PP |
fea681da | 24 | .fi |
d39ad78f | 25 | .RS -4 |
cc4615cc MK |
26 | Feature Test Macro Requirements for glibc (see |
27 | .BR feature_test_macros (7)): | |
d39ad78f | 28 | .RE |
68e4db0a | 29 | .PP |
9d2adbae | 30 | .nf |
caba2e47 | 31 | .BR log1p (): |
5c10d2c5 MK |
32 | _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L |
33 | || _XOPEN_SOURCE >= 500 | |
34 | .\" || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED | |
9d2adbae | 35 | || /* Since glibc 2.19: */ _DEFAULT_SOURCE |
75c018a1 | 36 | || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE |
9d2adbae | 37 | .fi |
98c9347c | 38 | .PP |
cc4615cc MK |
39 | .BR log1pf (), |
40 | .BR log1pl (): | |
9d2adbae | 41 | .nf |
5c10d2c5 | 42 | _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L |
9d2adbae | 43 | || /* Since glibc 2.19: */ _DEFAULT_SOURCE |
75c018a1 | 44 | || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE |
9d2adbae | 45 | .fi |
fea681da | 46 | .SH DESCRIPTION |
5600f73a | 47 | These functions return a value equivalent to |
207050fa | 48 | .PP |
2d986c92 | 49 | .nf |
2d986c92 | 50 | log (1 + \fIx\fP) |
2d986c92 | 51 | .fi |
207050fa | 52 | .PP |
5600f73a | 53 | The result is computed in a way |
022671eb MK |
54 | that is accurate even if the value of |
55 | .I x | |
56 | is near zero. | |
caba2e47 MK |
57 | .SH RETURN VALUE |
58 | On success, these functions return the natural logarithm of | |
59 | .IR "(1\ +\ x)" . | |
847e0d88 | 60 | .PP |
caba2e47 MK |
61 | If |
62 | .I x | |
63 | is a NaN, | |
64 | a NaN is returned. | |
847e0d88 | 65 | .PP |
caba2e47 MK |
66 | If |
67 | .I x | |
68 | is positive infinity, positive infinity is returned. | |
847e0d88 | 69 | .PP |
caba2e47 MK |
70 | If |
71 | .I x | |
efe294cb | 72 | is \-1, a pole error occurs, |
caba2e47 | 73 | and the functions return |
cd415e73 MK |
74 | .RB \- HUGE_VAL , |
75 | .RB \- HUGE_VALF , | |
caba2e47 | 76 | or |
cd415e73 | 77 | .RB \- HUGE_VALL , |
caba2e47 | 78 | respectively. |
847e0d88 | 79 | .PP |
caba2e47 MK |
80 | If |
81 | .I x | |
82 | is less than \-1 (including negative infinity), | |
efe294cb | 83 | a domain error occurs, |
caba2e47 MK |
84 | and a NaN (not a number) is returned. |
85 | .\" POSIX.1 specifies a possible range error if x is subnormal | |
86 | .\" glibc 2.8 doesn't do this | |
87 | .SH ERRORS | |
88 | See | |
89 | .BR math_error (7) | |
90 | for information on how to determine whether an error has occurred | |
91 | when calling these functions. | |
92 | .PP | |
93 | The following errors can occur: | |
94 | .TP | |
95 | Domain error: \fIx\fP is less than \-1 | |
523e7e59 AH |
96 | .I errno |
97 | is set to | |
1ae6b2c7 | 98 | .B EDOM |
523e7e59 | 99 | (but see BUGS). |
caba2e47 MK |
100 | An invalid floating-point exception |
101 | .RB ( FE_INVALID ) | |
102 | is raised. | |
103 | .TP | |
104 | Pole error: \fIx\fP is \-1 | |
523e7e59 AH |
105 | .I errno |
106 | is set to | |
1ae6b2c7 | 107 | .B ERANGE |
523e7e59 | 108 | (but see BUGS). |
caba2e47 MK |
109 | A divide-by-zero floating-point exception |
110 | .RB ( FE_DIVBYZERO ) | |
111 | is raised. | |
d05cb848 | 112 | .SH ATTRIBUTES |
eb71cf70 MK |
113 | For an explanation of the terms used in this section, see |
114 | .BR attributes (7). | |
115 | .TS | |
116 | allbox; | |
c466875e | 117 | lbx lb lb |
eb71cf70 MK |
118 | l l l. |
119 | Interface Attribute Value | |
120 | T{ | |
9e54434e BR |
121 | .na |
122 | .nh | |
d05cb848 PH |
123 | .BR log1p (), |
124 | .BR log1pf (), | |
d05cb848 | 125 | .BR log1pl () |
eb71cf70 MK |
126 | T} Thread safety MT-Safe |
127 | .TE | |
c466875e | 128 | .sp 1 |
3113c7f3 | 129 | .SH STANDARDS |
4131356c AC |
130 | C11, POSIX.1-2008. |
131 | .SH HISTORY | |
132 | C99, POSIX.1-2001. | |
caba2e47 | 133 | .\" BSD |
523e7e59 | 134 | .SH BUGS |
b324e17d | 135 | Before glibc 2.22, the glibc implementation did not set |
523e7e59 AH |
136 | .\" https://www.sourceware.org/bugzilla/show_bug.cgi?id=6792 |
137 | .I errno | |
138 | to | |
139 | .B EDOM | |
140 | when a domain error occurred. | |
847e0d88 | 141 | .PP |
b324e17d | 142 | Before glibc 2.22, the glibc implementation did not set |
523e7e59 AH |
143 | .\" https://www.sourceware.org/bugzilla/show_bug.cgi?id=6792 |
144 | .I errno | |
145 | to | |
146 | .B ERANGE | |
147 | when a range error occurred. | |
47297adb | 148 | .SH SEE ALSO |
fea681da MK |
149 | .BR exp (3), |
150 | .BR expm1 (3), | |
151 | .BR log (3) |