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Created after removing the erfc() material from erf.3. Documents the complementary error function.
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.so man3/erf.3
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.\" Copyright 2008, Linux Foundation, written by Michael Kerrisk
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.\" <mtk.manpages@gmail.com>
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.TH ERFC 3 2008-07-29 "GNU" "Linux Programmer's Manual"
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.SH NAME
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erfc, erfcf, erfcl \- complementary error function
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.SH SYNOPSIS
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.nf
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.B #include <math.h>
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.BI "double erfc(double " x );
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.BI "float erfcf(float " x );
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.BI "long double erfcl(long double " x );
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.fi
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Link with \fI\-lm\fP.
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.ad l
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.BR erfc ():
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_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE; or
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.I cc\ -std=c99
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.br
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.BR erfcf (),
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.BR erfcl ():
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_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600|| _ISOC99_SOURCE; or
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.I cc\ -std=c99
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.ad b
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.SH DESCRIPTION
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The
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.BR erfc ()
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function returns the complementary error function of
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.IR x ,
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that is, 1.0 \- erf(x).
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.SH RETURN VALUE
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On success, these functions return the complementary error function of
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.IR x ,
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a value in the range [0,2].
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If
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.I x
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is a NaN, a NaN is returned.
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If
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.I x
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is +0 or \-0, 1 is returned.
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If
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.I x
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is positive infinity,
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+0 is returned.
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If
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.I x
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is negative infinity,
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+2 is returned.
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If the function result underflows and produces an unrepresentable value,
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the return value is 0.0.
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If the function result underflows but produces a representable
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(i.e., subnormal) value,
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.\" e.g., erfc(27) on x86-32
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that value is returned, and
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a "range error" occurs.
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.SH ERRORS
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See
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.BR math_error (7)
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for information on how to determine whether an error has occurred
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when calling these functions.
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.PP
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The following errors can occur:
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.TP
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Range error: result underflow (result is subnormal)
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.\" .I errno
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.\" is set to
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.\" .BR ERANGE .
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An underflow floating-point exception
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.RB ( FE_UNDERFLOW )
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is raised.
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.PP
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These functions do not set
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.IR errno .
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.\" FIXME . Is it intentional that these functions do not set errno?
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.\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6785
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.SH "CONFORMING TO"
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C99, POSIX.1-2001.
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The variant returning
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.I double
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also conforms to
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SVr4, 4.3BSD.
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.SH NOTES
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The
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.BR erfc ()
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functions are provided to avoid the loss accuracy that
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would occur for the calculation 1-erf(x) for large values of
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.IR x
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(for which the value of erf(x) approaches 1).
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.SH "SEE ALSO"
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.BR cerf (3),
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.BR erf (3),
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.BR exp (3)
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