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)