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.

CONFORMING TO

       C99, POSIX.1-2001.  The variant returning double also conforms to SVr4, 4.3BSD.

NOTES

       The  erfc()  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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