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man:erfcl

ERFC(3) Linux Programmer's Manual ERFC(3)

NAME

`     erfc, erfcf, erfcl - complementary error function`

SYNOPSIS

`     #include <math.h>`
```     double erfc(double x);
float erfcf(float x);
long double erfcl(long double x);```
`     Link with -lm.`
` Feature Test Macro Requirements for glibc (see feature_test_macros(7)):`
```     erfc():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
erfcf(), erfcl():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE```

DESCRIPTION

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

RETURN VALUE

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

ERRORS

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

ATTRIBUTES

```     For   an   explanation   of   the  terms  used  in  this  section,  see
attributes(7).```
```     allbox; lbw24 lb  lb  l  l  l.   Interface Attribute Value  T{  erfc(),
erfcf(), erfcl() T}   Thread safety  MT-Safe```

CONFORMING TO

`     C99, POSIX.1-2001, POSIX.1-2008.`
`     The variant returning double also conforms to SVr4, 4.3BSD.`

NOTES

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

`     cerf(3), erf(3), exp(3)`

COLOPHON

```     This  page  is  part of release 4.16 of the Linux man-pages project.  A
description of the project, information about reporting bugs,  and  the
latest     version     of     this    page,    can    be    found    at
https://www.kernel.org/doc/man-pages/.```

GNU 2017-09-15 ERFC(3)