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erfc(3)


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

CONFORMING TO

   C99, POSIX.1-2001, POSIX.1-2008.

   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

   This  page  is  part of release 4.09 of the Linux man-pages project.  A
   description of the project, information about reporting bugs,  and  the
   latest     version     of     this    page,    can    be    found    at
   https://www.kernel.org/doc/man-pages/.



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