erfc(3) - f38

1erfc(3)                    Library Functions Manual                    erfc(3)
2
3
4

NAME

6       erfc, erfcf, erfcl - complementary error function
7

LIBRARY

9       Math library (libm, -lm)
10

SYNOPSIS

12       #include <math.h>
13
14       double erfc(double x);
15       float erfcf(float x);
16       long double erfcl(long double x);
17
18   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
19
20       erfc():
21           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE
22               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
23               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
24
25       erfcf(), erfcl():
26           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
27               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
28               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
29

DESCRIPTION

31       These  functions return the complementary error function of x, that is,
32       1.0 - erf(x).
33

RETURN VALUE

35       On success, these functions return the complementary error function  of
36       x, a value in the range [0,2].
37
38       If x is a NaN, a NaN is returned.
39
40       If x is +0 or -0, 1 is returned.
41
42       If x is positive infinity, +0 is returned.
43
44       If x is negative infinity, +2 is returned.
45
46       If  the  function  result  underflows  and  produces an unrepresentable
47       value, the return value is 0.0.
48
49       If the function result underflows but produces a  representable  (i.e.,
50       subnormal) value, that value is returned, and a range error occurs.
51

ERRORS

53       See  math_error(7) for information on how to determine whether an error
54       has occurred when calling these functions.
55
56       The following errors can occur:
57
58       Range error: result underflow (result is subnormal)
59              An underflow floating-point exception (FE_UNDERFLOW) is raised.
60
61       These functions do not set errno.
62

ATTRIBUTES

64       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
65       tributes(7).
66
67       ┌────────────────────────────────────────────┬───────────────┬─────────┐
68       │Interface                                   │ Attribute     │ Value   │
69       ├────────────────────────────────────────────┼───────────────┼─────────┤
70       │erfc(), erfcf(), erfcl()                    │ Thread safety │ MT-Safe │
71       └────────────────────────────────────────────┴───────────────┴─────────┘
72

STANDARDS

74       C11, POSIX.1-2008.
75

HISTORY

77       C99, POSIX.1-2001.
78
79       The variant returning double also conforms to SVr4, 4.3BSD.
80

NOTES

82       The  erfc(),  erfcf(),  and erfcl() functions are provided to avoid the
83       loss accuracy that would occur for the calculation 1-erf(x)  for  large
84       values of x (for which the value of erf(x) approaches 1).
85