1ERFC(3)                    Linux Programmer's Manual                   ERFC(3)
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NAME

6       erfc, erfcf, erfcl - complementary error function
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SYNOPSIS

9       #include <math.h>
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11       double erfc(double x);
12       float erfcf(float x);
13       long double erfcl(long double x);
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15       Link with -lm.
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17   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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19       erfc(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE;
20       or cc -std=c99
21       erfcf(), erfcl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600||
22       _ISOC99_SOURCE; or cc -std=c99
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DESCRIPTION

25       The erfc() function returns the complementary error function of x, that
26       is, 1.0 - erf(x).
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RETURN VALUE

29       On success, these functions return the complementary error function  of
30       x, a value in the range [0,2].
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32       If x is a NaN, a NaN is returned.
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34       If x is +0 or -0, 1 is returned.
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36       If x is positive infinity, +0 is returned.
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38       If x is negative infinity, +2 is returned.
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40       If  the  function  result  underflows  and  produces an unrepresentable
41       value, the return value is 0.0.
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43       If the function result underflows but produces a  representable  (i.e.,
44       subnormal) value, that value is returned, and a range error occurs.
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ERRORS

47       See  math_error(7) for information on how to determine whether an error
48       has occurred when calling these functions.
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50       The following errors can occur:
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52       Range error: result underflow (result is subnormal)
53              An underflow floating-point exception (FE_UNDERFLOW) is raised.
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55       These functions do not set errno.
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CONFORMING TO

58       C99, POSIX.1-2001.  The variant returning double also conforms to SVr4,
59       4.3BSD.
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NOTES

62       The erfc() functions are provided to avoid the loss accuracy that would
63       occur for the calculation 1-erf(x) for large values of x (for which the
64       value of erf(x) approaches 1).
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SEE ALSO

67       cerf(3), erf(3), exp(3)
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COLOPHON

70       This  page  is  part of release 3.25 of the Linux man-pages project.  A
71       description of the project, and information about reporting  bugs,  can
72       be found at http://www.kernel.org/doc/man-pages/.
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76GNU                               2008-08-05                           ERFC(3)
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