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+'\" t
+.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
+.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
+.\"     <mtk.manpages@gmail.com>
+.\"
+.\" SPDX-License-Identifier: Linux-man-pages-copyleft
+.\"
+.\" References consulted:
+.\"     Linux libc source code
+.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
+.\"     386BSD man pages
+.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
+.\" Modified 2002-07-27 by Walter Harms
+.\" 	(walter.harms@informatik.uni-oldenburg.de)
+.\"
+.TH erf 3 2023-07-20 "Linux man-pages 6.05.01"
+.SH NAME
+erf, erff, erfl \- error function
+.SH LIBRARY
+Math library
+.RI ( libm ", " \-lm )
+.SH SYNOPSIS
+.nf
+.B #include <math.h>
+.PP
+.BI "double erf(double " x );
+.BI "float erff(float " x );
+.BI "long double erfl(long double " x );
+.PP
+.fi
+.RS -4
+Feature Test Macro Requirements for glibc (see
+.BR feature_test_macros (7)):
+.RE
+.PP
+.BR erf ():
+.nf
+    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE
+        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
+        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
+.fi
+.PP
+.BR erff (),
+.BR erfl ():
+.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 error function of
+.IR x ,
+defined as
+.PP
+.in +4n
+.EX
+erf(x) = 2/sqrt(pi) * integral from 0 to x of exp(\-t*t) dt
+.EE
+.in
+.SH RETURN VALUE
+On success, these functions return the value of the error function of
+.IR x ,
+a value in the range [\-1,\ 1].
+.PP
+If
+.I x
+is a NaN, a NaN is returned.
+.PP
+If
+.I x
+is +0 (\-0), +0 (\-0) is returned.
+.PP
+If
+.I x
+is positive infinity (negative infinity),
++1 (\-1) is returned.
+.PP
+If
+.I x
+is subnormal,
+a range error occurs,
+and the return value is 2*x/sqrt(pi).
+.SH ERRORS
+See
+.BR math_error (7)
+for information on how to determine whether an error has occurred
+when calling these functions.
+.PP
+The following errors can occur:
+.TP
+Range error: result underflow (\fIx\fP is subnormal)
+.\" .I errno
+.\" is set to
+.\" .BR ERANGE .
+An underflow floating-point exception
+.RB ( FE_UNDERFLOW )
+is raised.
+.PP
+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 erf (),
+.BR erff (),
+.BR erfl ()
+T}	Thread safety	MT-Safe
+.TE
+.sp 1
+.SH STANDARDS
+C11, POSIX.1-2008.
+.SH HISTORY
+C99, POSIX.1-2001.
+.PP
+The variant returning
+.I double
+also conforms to
+SVr4, 4.3BSD.
+.SH SEE ALSO
+.BR cerf (3),
+.BR erfc (3),
+.BR exp (3)