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
12 erfc, erfcf, erfcl — complementary error functions
13
15 #include <math.h>
16 double erfc(double x);
18 float erfcf(float x);
19 long double erfcl(long double x);
20
22 The functionality described on this reference page is aligned with the
23 ISO C standard. Any conflict between the requirements described here
24 and the ISO C standard is unintentional. This volume of POSIX.1‐2017
25 defers to the ISO C standard.
26 These functions shall compute the complementary error function 1.0 -
28 erf(x).
29 An application wishing to check for error situations should set errno
31 to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
32 functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
33 FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
34 occurred.
35
37 Upon successful completion, these functions shall return the value of
38 the complementary error function.
39 If the correct value would cause underflow, and is not representable, a
41 range error may occur, and erfc(), erfcf(), and erfcl() shall return
42 0.0, or (if the IEC 60559 Floating-Point option is not supported) an
43 implementation-defined value no greater in magnitude than DBL_MIN,
44 FLT_MIN, and LDBL_MIN, respectively.
45 If x is NaN, a NaN shall be returned.
47 If x is ±0, +1 shall be returned.
49 If x is -Inf, +2 shall be returned.
51 If x is +Inf, +0 shall be returned.
53 If the correct value would cause underflow and is representable, a
55 range error may occur and the correct value shall be returned.
56
58 These functions may fail if:
59 Range Error The result underflows.
61 If the integer expression (math_errhandling & MATH_ERRNO)
63 is non-zero, then errno shall be set to [ERANGE]. If the
64 integer expression (math_errhandling & MATH_ERREXCEPT) is
65 non-zero, then the underflow floating-point exception shall
66 be raised.
67 The following sections are informative.
69
71 None.
72
74 The erfc() function is provided because of the extreme loss of relative
75 accuracy if erf(x) is called for large x and the result subtracted from
76 1.0.
77 On error, the expressions (math_errhandling & MATH_ERRNO) and
79 (math_errhandling & MATH_ERREXCEPT) are independent of each other, but
80 at least one of them must be non-zero.
81
83 None.
84
86 None.
87
89 erf(), feclearexcept(), fetestexcept(), isnan()
90 The Base Definitions volume of POSIX.1‐2017, Section 4.20, Treatment of
92 Error Conditions for Mathematical Functions, <math.h>
93
95 Portions of this text are reprinted and reproduced in electronic form
96 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
97 table Operating System Interface (POSIX), The Open Group Base Specifi‐
98 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
99 Electrical and Electronics Engineers, Inc and The Open Group. In the
100 event of any discrepancy between this version and the original IEEE and
101 The Open Group Standard, the original IEEE and The Open Group Standard
102 is the referee document. The original Standard can be obtained online
103 at http://www.opengroup.org/unix/online.html .
104 Any typographical or formatting errors that appear in this page are
106 most likely to have been introduced during the conversion of the source
107 files to man page format. To report such errors, see https://www.ker‐
108 nel.org/doc/man-pages/reporting_bugs.html .
109IEEE/The Open Group 2017 ERFC(3P)