1ERFC(3P) POSIX Programmer's Manual ERFC(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 erfc, erfcf, erfcl — complementary error functions
14
16 #include <math.h>
17 double erfc(double x);
19 float erfcf(float x);
20 long double erfcl(long double x);
21
23 The functionality described on this reference page is aligned with the
24 ISO C standard. Any conflict between the requirements described here
25 and the ISO C standard is unintentional. This volume of POSIX.1‐2008
26 defers to the ISO C standard.
27 These functions shall compute the complementary error function 1.0 −
29 erf(x).
30 An application wishing to check for error situations should set errno
32 to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
33 functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
34 FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
35 occurred.
36
38 Upon successful completion, these functions shall return the value of
39 the complementary error function.
40 If the correct value would cause underflow, and is not representable, a
42 range error may occur, and erfc(), erfcf(), and erfcl() shall return
43 0.0, or (if the IEC 60559 Floating-Point option is not supported) an
44 implementation-defined value no greater in magnitude than DBL_MIN,
45 FLT_MIN, and LDBL_MIN, respectively.
46 If x is NaN, a NaN shall be returned.
48 If x is ±0, +1 shall be returned.
50 If x is −Inf, +2 shall be returned.
52 If x is +Inf, +0 shall be returned.
54 If the correct value would cause underflow and is representable, a
56 range error may occur and the correct value shall be returned.
57
59 These functions may fail if:
60 Range Error The result underflows.
62 If the integer expression (math_errhandling & MATH_ERRNO)
64 is non-zero, then errno shall be set to [ERANGE]. If the
65 integer expression (math_errhandling & MATH_ERREXCEPT) is
66 non-zero, then the underflow floating-point exception shall
67 be raised.
68 The following sections are informative.
70
72 None.
73
75 The erfc() function is provided because of the extreme loss of relative
76 accuracy if erf(x) is called for large x and the result subtracted from
77 1.0.
78 Note for IEEE Std 754‐1985 double, 26.55 < x implies erfc(x) has under‐
80 flowed.
81 On error, the expressions (math_errhandling & MATH_ERRNO) and
83 (math_errhandling & MATH_ERREXCEPT) are independent of each other, but
84 at least one of them must be non-zero.
85
87 None.
88
90 None.
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93 erf(), feclearexcept(), fetestexcept(), isnan()
94 The Base Definitions volume of POSIX.1‐2008, Section 4.19, Treatment of
96 Error Conditions for Mathematical Functions, <math.h>
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99 Portions of this text are reprinted and reproduced in electronic form
100 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
101 -- Portable Operating System Interface (POSIX), The Open Group Base
102 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
103 cal and Electronics Engineers, Inc and The Open Group. (This is
104 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
105 event of any discrepancy between this version and the original IEEE and
106 The Open Group Standard, the original IEEE and The Open Group Standard
107 is the referee document. The original Standard can be obtained online
108 at http://www.unix.org/online.html .
109 Any typographical or formatting errors that appear in this page are
111 most likely to have been introduced during the conversion of the source
112 files to man page format. To report such errors, see https://www.ker‐
113 nel.org/doc/man-pages/reporting_bugs.html .
114IEEE/The Open Group 2013 ERFC(3P)