erfc(3)                    Library Functions Manual                    erfc(3)

NAME
       erfc, erfcf, erfcl - complementary error function

LIBRARY
       Math library (libm, -lm)

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

       erfcf(), erfcl():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* 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).

       +--------------------------------------------+---------------+---------+
       |Interface                                   | Attribute     | Value   |
       +--------------------------------------------+---------------+---------+
       |erfc (), erfcf (), erfcl ()                 | Thread safety | MT-Safe |
       +--------------------------------------------+---------------+---------+
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)

Linux man-pages 6.7               2023-10-31                           erfc(3)