SIMPLE SOLUTIONS

# ERFC(3) - man page online | library functions

Complementary error function.

Chapter
2015-04-19
```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);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

erfc():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99
erfcf(), erfcl():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600|| _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99

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).

┌─────────────────────────┬───────────────┬─────────┐
│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).