.\" Modified 2002-07-27 by Walter Harms
.\" (walter.harms@informatik.uni-oldenburg.de)
.\"
-.TH ERF 3 2015-04-19 "GNU" "Linux Programmer's Manual"
+.TH ERF 3 2017-09-15 "GNU" "Linux Programmer's Manual"
.SH NAME
-erf, erff, erfl, \- error function
+erf, erff, erfl \- error function
.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
Link with \fI\-lm\fP.
-.sp
+.PP
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
-.sp
+.PP
.ad l
.BR erf ():
.RS 4
-_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE ||
-_POSIX_C_SOURCE\ >=\ 200112L
-.br
-or
-.I cc\ -std=c99
+_ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L || _XOPEN_SOURCE
+ || /* Since glibc 2.19: */ _DEFAULT_SOURCE
+ || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.RE
.br
.BR erff (),
.BR erfl ():
.RS 4
-_BSD_SOURCE || _SVID_SOURCE || _ISOC99_SOURCE ||
-_POSIX_C_SOURCE\ >=\ 200112L
-.br
-or
-.I cc\ -std=c99
+_ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
+ || /* Since glibc 2.19: */ _DEFAULT_SOURCE
+ || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.RE
.ad b
.SH DESCRIPTION
.IR x ,
defined as
.TP
- erf(x) = 2/sqrt(pi)* integral from 0 to x of exp(\-t*t) dt
+ erf(x) = 2/sqrt(pi) * integral from 0 to x of exp(\-t*t) dt
.SH RETURN VALUE
-On success, these functions return the error function of
+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,
.PP
These functions do not set
.IR errno .
-.\" FIXME . Is it intentional that these functions do not set errno?
-.\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6785
+.\" It is intentional that these functions do not set errno for this case
+.\" see http://sources.redhat.com/bugzilla/show_bug.cgi?id=6785
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TE
.SH CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008.
-
+.PP
The variant returning
.I double
also conforms to