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ERFC(3)                    Linux Programmer's Manual                   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(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE; or cc -std=c99
       erfcf(), erfcl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600|| _ISOC99_SOURCE; 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  func-
       tions.

       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
       This page is part of release 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



GNU                               2008-08-05                           ERFC(3)