1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
2 .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
3 .\" <mtk.manpages@gmail.com>
5 .\" %%%LICENSE_START(VERBATIM)
6 .\" Permission is granted to make and distribute verbatim copies of this
7 .\" manual provided the copyright notice and this permission notice are
8 .\" preserved on all copies.
10 .\" Permission is granted to copy and distribute modified versions of this
11 .\" manual under the conditions for verbatim copying, provided that the
12 .\" entire resulting derived work is distributed under the terms of a
13 .\" permission notice identical to this one.
15 .\" Since the Linux kernel and libraries are constantly changing, this
16 .\" manual page may be incorrect or out-of-date. The author(s) assume no
17 .\" responsibility for errors or omissions, or for damages resulting from
18 .\" the use of the information contained herein. The author(s) may not
19 .\" have taken the same level of care in the production of this manual,
20 .\" which is licensed free of charge, as they might when working
23 .\" Formatted or processed versions of this manual, if unaccompanied by
24 .\" the source, must acknowledge the copyright and authors of this work.
27 .\" References consulted:
28 .\" Linux libc source code
29 .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
31 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
32 .\" Modified 2002-07-27 by Walter Harms
33 .\" (walter.harms@informatik.uni-oldenburg.de)
35 .TH ERF 3 2017-09-15 "GNU" "Linux Programmer's Manual"
37 erf, erff, erfl, \- error function
42 .BI "double erf(double " x );
43 .BI "float erff(float " x );
44 .BI "long double erfl(long double " x );
50 Feature Test Macro Requirements for glibc (see
51 .BR feature_test_macros (7)):
57 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L || _XOPEN_SOURCE
58 || /* Since glibc 2.19: */ _DEFAULT_SOURCE
59 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
65 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
66 || /* Since glibc 2.19: */ _DEFAULT_SOURCE
67 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
71 These functions return the error function of
75 erf(x) = 2/sqrt(pi)* integral from 0 to x of exp(\-t*t) dt
77 On success, these functions return the error function of
79 a value in the range [\-1,\ 1].
83 is a NaN, a NaN is returned.
87 is +0 (\-0), +0 (\-0) is returned.
91 is positive infinity (negative infinity),
98 and the return value is 2*x/sqrt(pi).
102 for information on how to determine whether an error has occurred
103 when calling these functions.
105 The following errors can occur:
107 Range error: result underflow (\fIx\fP is subnormal)
111 An underflow floating-point exception
115 These functions do not set
117 .\" FIXME . Is it intentional that these functions do not set errno?
118 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6785
120 For an explanation of the terms used in this section, see
126 Interface Attribute Value
131 T} Thread safety MT-Safe
134 C99, POSIX.1-2001, POSIX.1-2008.
136 The variant returning