**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 at-
**tributes(7)**.
+-------------------------+---------------+---------+
|Interface | Attribute | Value |
+-------------------------+---------------+---------+
|erfc(), erfcf(), erfcl() | 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).
SEE ALSO
**cerf(3)**, **erf(3)**, **exp(3)**
COLOPHON
This page is part of release 5.05 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)**

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