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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():

_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

The erfc() function returns 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

Multithreading (see pthreads(7) )

The erfc(), erfcf(), and erfcl() functions are thread-safe.

Conforming to

C99, POSIX.1-2001. 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

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