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1 | .\" Copyright 2008, Linux Foundation, written by Michael Kerrisk |
2 | .\" <mtk.manpages@gmail.com> | |
3 | .\" | |
4b72fb64 | 4 | .\" %%%LICENSE_START(verbatim) |
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5 | .\" Permission is granted to make and distribute verbatim copies of this |
6 | .\" manual provided the copyright notice and this permission notice are | |
7 | .\" preserved on all copies. | |
8 | .\" | |
9 | .\" Permission is granted to copy and distribute modified versions of this | |
10 | .\" manual under the conditions for verbatim copying, provided that the | |
11 | .\" entire resulting derived work is distributed under the terms of a | |
12 | .\" permission notice identical to this one. | |
13 | .\" | |
14 | .\" Since the Linux kernel and libraries are constantly changing, this | |
15 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
16 | .\" responsibility for errors or omissions, or for damages resulting from | |
17 | .\" the use of the information contained herein. The author(s) may not | |
18 | .\" have taken the same level of care in the production of this manual, | |
19 | .\" which is licensed free of charge, as they might when working | |
20 | .\" professionally. | |
21 | .\" | |
22 | .\" Formatted or processed versions of this manual, if unaccompanied by | |
23 | .\" the source, must acknowledge the copyright and authors of this work. | |
4b72fb64 | 24 | .\" %%%LICENSE_END |
1521a504 | 25 | .\" |
50831f9b | 26 | .TH ERFC 3 2010-09-20 "GNU" "Linux Programmer's Manual" |
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27 | .SH NAME |
28 | erfc, erfcf, erfcl \- complementary error function | |
29 | .SH SYNOPSIS | |
30 | .nf | |
31 | .B #include <math.h> | |
32 | ||
33 | .BI "double erfc(double " x ); | |
34 | .BI "float erfcf(float " x ); | |
35 | .BI "long double erfcl(long double " x ); | |
36 | ||
37 | .fi | |
38 | Link with \fI\-lm\fP. | |
39 | .sp | |
40 | .in -4n | |
41 | Feature Test Macro Requirements for glibc (see | |
42 | .BR feature_test_macros (7)): | |
43 | .in | |
44 | .sp | |
45 | .ad l | |
46 | .BR erfc (): | |
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47 | .RS 4 |
48 | _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE || | |
49 | _POSIX_C_SOURCE\ >=\ 200112L; | |
50 | .br | |
51 | or | |
1521a504 | 52 | .I cc\ -std=c99 |
14d23282 | 53 | .RE |
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54 | .br |
55 | .BR erfcf (), | |
56 | .BR erfcl (): | |
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57 | .RS 4 |
58 | _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600|| _ISOC99_SOURCE || | |
59 | _POSIX_C_SOURCE\ >=\ 200112L; | |
60 | .br | |
61 | or | |
1521a504 | 62 | .I cc\ -std=c99 |
14d23282 | 63 | .RE |
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64 | .ad b |
65 | .SH DESCRIPTION | |
66 | The | |
67 | .BR erfc () | |
68 | function returns the complementary error function of | |
69 | .IR x , | |
70 | that is, 1.0 \- erf(x). | |
71 | .SH RETURN VALUE | |
72 | On success, these functions return the complementary error function of | |
73 | .IR x , | |
74 | a value in the range [0,2]. | |
75 | ||
76 | If | |
77 | .I x | |
78 | is a NaN, a NaN is returned. | |
79 | ||
80 | If | |
81 | .I x | |
82 | is +0 or \-0, 1 is returned. | |
83 | ||
84 | If | |
85 | .I x | |
86 | is positive infinity, | |
87 | +0 is returned. | |
88 | ||
89 | If | |
90 | .I x | |
91 | is negative infinity, | |
92 | +2 is returned. | |
93 | ||
94 | If the function result underflows and produces an unrepresentable value, | |
95 | the return value is 0.0. | |
96 | ||
97 | If the function result underflows but produces a representable | |
98 | (i.e., subnormal) value, | |
99 | .\" e.g., erfc(27) on x86-32 | |
100 | that value is returned, and | |
efe294cb | 101 | a range error occurs. |
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102 | .SH ERRORS |
103 | See | |
104 | .BR math_error (7) | |
105 | for information on how to determine whether an error has occurred | |
106 | when calling these functions. | |
107 | .PP | |
108 | The following errors can occur: | |
109 | .TP | |
110 | Range error: result underflow (result is subnormal) | |
111 | .\" .I errno | |
112 | .\" is set to | |
113 | .\" .BR ERANGE . | |
114 | An underflow floating-point exception | |
115 | .RB ( FE_UNDERFLOW ) | |
116 | is raised. | |
117 | .PP | |
118 | These functions do not set | |
119 | .IR errno . | |
120 | .\" FIXME . Is it intentional that these functions do not set errno? | |
121 | .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6785 | |
47297adb | 122 | .SH CONFORMING TO |
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123 | C99, POSIX.1-2001. |
124 | The variant returning | |
125 | .I double | |
126 | also conforms to | |
127 | SVr4, 4.3BSD. | |
128 | .SH NOTES | |
129 | The | |
130 | .BR erfc () | |
131 | functions are provided to avoid the loss accuracy that | |
132 | would occur for the calculation 1-erf(x) for large values of | |
133 | .IR x | |
134 | (for which the value of erf(x) approaches 1). | |
47297adb | 135 | .SH SEE ALSO |
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136 | .BR cerf (3), |
137 | .BR erf (3), | |
138 | .BR exp (3) |