erfc, erfcf, erfcl - complementary error function
#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
These functions return the complementary error function of
x, that is,
1.0 - erf(x).
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.
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.
For an explanation of the terms used in this section, see
attributes(7).
Interface |
Attribute |
Value |
erfc (), erfcf (), erfcl () |
Thread safety |
MT-Safe |
C99, POSIX.1-2001, POSIX.1-2008.
The variant returning
double also conforms to SVr4, 4.3BSD.
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)