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+'\" t
+.\" Copyright 2008, Linux Foundation, written by Michael Kerrisk
+.\"     <mtk.manpages@gmail.com>
+.\"
+.\" SPDX-License-Identifier: Linux-man-pages-copyleft
+.\"
+.TH erfc 3 2024-05-02 "Linux man-pages (unreleased)"
+.SH NAME
+erfc, erfcf, erfcl \- complementary error function
+.SH LIBRARY
+Math library
+.RI ( libm ", " \-lm )
+.SH SYNOPSIS
+.nf
+.B #include <math.h>
+.P
+.BI "double erfc(double " x );
+.BI "float erfcf(float " x );
+.BI "long double erfcl(long double " x );
+.fi
+.P
+.RS -4
+Feature Test Macro Requirements for glibc (see
+.BR feature_test_macros (7)):
+.RE
+.P
+.BR erfc ():
+.nf
+    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE
+        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
+        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
+.fi
+.P
+.BR erfcf (),
+.BR erfcl ():
+.nf
+    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
+        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
+        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
+.fi
+.SH DESCRIPTION
+These functions return the complementary error function of
+.IR x ,
+that is, 1.0 \- erf(x).
+.SH RETURN VALUE
+On success, these functions return the complementary error function of
+.IR x ,
+a value in the range [0,2].
+.P
+If
+.I x
+is a NaN, a NaN is returned.
+.P
+If
+.I x
+is +0 or \-0, 1 is returned.
+.P
+If
+.I x
+is positive infinity,
++0 is returned.
+.P
+If
+.I x
+is negative infinity,
++2 is returned.
+.P
+If the function result underflows and produces an unrepresentable value,
+the return value is 0.0.
+.P
+If the function result underflows but produces a representable
+(i.e., subnormal) value,
+.\" e.g., erfc(27) on x86-32
+that value is returned, and
+a range error occurs.
+.SH ERRORS
+See
+.BR math_error (7)
+for information on how to determine whether an error has occurred
+when calling these functions.
+.P
+The following errors can occur:
+.TP
+Range error: result underflow (result is subnormal)
+.\" .I errno
+.\" is set to
+.\" .BR ERANGE .
+An underflow floating-point exception
+.RB ( FE_UNDERFLOW )
+is raised.
+.P
+These functions do not set
+.IR errno .
+.\" It is intentional that these functions do not set errno for this case
+.\" see https://www.sourceware.org/bugzilla/show_bug.cgi?id=6785
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.TS
+allbox;
+lbx lb lb
+l l l.
+Interface	Attribute	Value
+T{
+.na
+.nh
+.BR erfc (),
+.BR erfcf (),
+.BR erfcl ()
+T}	Thread safety	MT-Safe
+.TE
+.SH STANDARDS
+C11, POSIX.1-2008.
+.SH HISTORY
+C99, POSIX.1-2001.
+.P
+The variant returning
+.I double
+also conforms to
+SVr4, 4.3BSD.
+.SH NOTES
+The
+.BR erfc (),
+.BR erfcf (),
+and
+.BR erfcl ()
+functions are provided to avoid the loss accuracy that
+would occur for the calculation 1-erf(x) for large values of
+.I x
+(for which the value of erf(x) approaches 1).
+.SH SEE ALSO
+.BR cerf (3),
+.BR erf (3),
+.BR exp (3)