erfc(3)

NAME#

erfc, erfcf, erfcl - complementary error function

LIBRARY#

Math library (libm, -lm)

SYNOPSIS#

#include <math.h>

double erfc(double \nx\n);\n
\nfloat erfcf(float \nx\n);\n
\nlong double erfcl(long double \nx\n);

erfc():

\n
    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE
\n
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
\n
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

erfcf(), erfcl():

\n
    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
\n
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
\n
        || /* glibc <= 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).

STANDARDS#

C11, POSIX.1-2008.

HISTORY#

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)