erfc(3) - f39

1erfc(3)                    Library Functions Manual                    erfc(3)
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NAME

6       erfc, erfcf, erfcl - complementary error function
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LIBRARY

9       Math library (libm, -lm)
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SYNOPSIS

12       #include <math.h>
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14       double erfc(double x);
15       float erfcf(float x);
16       long double erfcl(long double x);
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18   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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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
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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
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DESCRIPTION

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

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

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

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

74       C11, POSIX.1-2008.
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HISTORY

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