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fea681da | 1 | .\" Copyright 1995 Jim Van Zandt <jrv@vanzandt.mv.com> |
77c9946a 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16 | .\" manual page may be incorrect or out-of-date.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 Walter Harms | |
28 | .\" (walter.harms@informatik.uni-oldenburg.de) | |
29 | .\" | |
4b8c67d9 | 30 | .TH EXPM1 3 2017-09-15 "" "Linux Programmer's Manual" |
fea681da | 31 | .SH NAME |
77c9946a | 32 | expm1, expm1f, expm1l \- exponential minus 1 |
fea681da MK |
33 | .SH SYNOPSIS |
34 | .nf | |
35 | .B #include <math.h> | |
68e4db0a | 36 | .PP |
fea681da | 37 | .BI "double expm1(double " x ); |
fea681da | 38 | .BI "float expm1f(float " x ); |
fea681da | 39 | .BI "long double expm1l(long double " x ); |
68e4db0a | 40 | .PP |
fea681da | 41 | .fi |
20c58d70 | 42 | Link with \fI\-lm\fP. |
68e4db0a | 43 | .PP |
cc4615cc MK |
44 | .in -4n |
45 | Feature Test Macro Requirements for glibc (see | |
46 | .BR feature_test_macros (7)): | |
47 | .in | |
68e4db0a | 48 | .PP |
cc4615cc | 49 | .ad l |
77c9946a | 50 | .BR expm1 (): |
810e18c2 | 51 | .RS 4 |
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52 | _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L |
53 | || _XOPEN_SOURCE\ >=\ 500 | |
cf7fa0a1 | 54 | .\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED |
636ed4d5 MK |
55 | || /* Since glibc 2.19: */ _DEFAULT_SOURCE |
56 | || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE | |
810e18c2 | 57 | .RE |
77c9946a | 58 | .br |
cc4615cc MK |
59 | .BR expm1f (), |
60 | .BR expm1l (): | |
810e18c2 | 61 | .RS 4 |
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62 | _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L |
63 | || /* Since glibc 2.19: */ _DEFAULT_SOURCE | |
64 | || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE | |
810e18c2 | 65 | .RE |
cc4615cc | 66 | .ad b |
fea681da | 67 | .SH DESCRIPTION |
5600f73a | 68 | These functions return a value equivalent to |
207050fa | 69 | .PP |
8937ead2 | 70 | .nf |
8937ead2 | 71 | exp(x) \- 1 |
8937ead2 | 72 | .fi |
207050fa | 73 | .PP |
5600f73a | 74 | The result is computed in a way that is accurate even if the value of |
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75 | .I x |
76 | is near | |
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77 | zero\(ema case where |
78 | .I "exp(x) \- 1" | |
79 | would be inaccurate due to | |
fea681da | 80 | subtraction of two numbers that are nearly equal. |
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81 | .SH RETURN VALUE |
82 | On success, these functions return | |
83 | .IR "exp(x)\ \-\ 1" . | |
847e0d88 | 84 | .PP |
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85 | If |
86 | .I x | |
87 | is a NaN, | |
88 | a NaN is returned. | |
847e0d88 | 89 | .PP |
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90 | If |
91 | .I x | |
92 | is +0 (\-0), | |
93 | +0 (\-0) is returned. | |
847e0d88 | 94 | .PP |
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95 | If |
96 | .I x | |
97 | is positive infinity, positive infinity is returned. | |
847e0d88 | 98 | .PP |
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99 | If |
100 | .I x | |
101 | is negative infinity, \-1 is returned. | |
847e0d88 | 102 | .PP |
efe294cb | 103 | If the result overflows, a range error occurs, |
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104 | and the functions return |
105 | .RB - HUGE_VAL , | |
106 | .RB - HUGE_VALF , | |
107 | or | |
108 | .RB - HUGE_VALL , | |
109 | respectively. | |
110 | .SH ERRORS | |
111 | See | |
112 | .BR math_error (7) | |
113 | for information on how to determine whether an error has occurred | |
114 | when calling these functions. | |
115 | .PP | |
116 | The following errors can occur: | |
117 | .TP | |
118 | Range error, overflow | |
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119 | .I errno |
120 | is set to | |
121 | .BR ERANGE | |
122 | (but see BUGS). | |
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123 | An overflow floating-point exception |
124 | .RB ( FE_OVERFLOW ) | |
125 | is raised. | |
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126 | .\" |
127 | .\" POSIX.1 specifies an optional range error (underflow) if | |
128 | .\" x is subnormal. Glibc does not implement this. | |
a2f0602b | 129 | .SH ATTRIBUTES |
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130 | For an explanation of the terms used in this section, see |
131 | .BR attributes (7). | |
132 | .TS | |
133 | allbox; | |
134 | lbw27 lb lb | |
135 | l l l. | |
136 | Interface Attribute Value | |
137 | T{ | |
a2f0602b PH |
138 | .BR expm1 (), |
139 | .BR expm1f (), | |
a2f0602b | 140 | .BR expm1l () |
f0908802 MK |
141 | T} Thread safety MT-Safe |
142 | .TE | |
47297adb | 143 | .SH CONFORMING TO |
9a74e018 | 144 | C99, POSIX.1-2001, POSIX.1-2008. |
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145 | .\" BSD. |
146 | .SH BUGS | |
147 | For some large negative | |
148 | .I x | |
19dffabe | 149 | values (where the function result approaches \-1), |
77c9946a | 150 | .BR expm1 () |
0b9fe528 | 151 | raises a bogus underflow floating-point exception. |
19dffabe | 152 | .\" FIXME . |
77c9946a | 153 | .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6778 |
847e0d88 | 154 | .PP |
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155 | For some large positive |
156 | .I x | |
157 | values, | |
158 | .BR expm1 () | |
0b9fe528 | 159 | raises a bogus invalid floating-point exception in addition to the expected |
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160 | overflow exception, and returns a NaN instead of positive infinity. |
161 | .\" FIXME . | |
162 | .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6814 | |
163 | .\" e.g., expm1(1e5) through expm1(1.00199970127e5), | |
164 | .\" but not expm1(1.00199970128e5) and beyond. | |
847e0d88 | 165 | .PP |
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166 | Before version 2.11, |
167 | .\" It looks like the fix was in 2.11, or possibly 2.12. | |
168 | .\" I have no test system for 2.11, but 2.12 passes. | |
169 | .\" From the source (sysdeps/i386/fpu/s_expm1.S) it looks | |
170 | .\" like the changes were in 2.11. | |
171 | the glibc implementation did not set | |
172 | .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6788 | |
173 | .I errno | |
174 | to | |
175 | .B ERANGE | |
176 | when a range error occurred. | |
47297adb | 177 | .SH SEE ALSO |
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178 | .BR exp (3), |
179 | .BR log (3), | |
180 | .BR log1p (3) |