1
/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
3
* ***** BEGIN LICENSE BLOCK *****
4
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
6
* The contents of this file are subject to the Mozilla Public License Version
7
* 1.1 (the "License"); you may not use this file except in compliance with
8
* the License. You may obtain a copy of the License at
9
* http://www.mozilla.org/MPL/
11
* Software distributed under the License is distributed on an "AS IS" basis,
12
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
13
* for the specific language governing rights and limitations under the
16
* The Original Code is Mozilla Communicator client code, released
19
* The Initial Developer of the Original Code is
20
* Sun Microsystems, Inc.
21
* Portions created by the Initial Developer are Copyright (C) 1998
22
* the Initial Developer. All Rights Reserved.
26
* Alternatively, the contents of this file may be used under the terms of
27
* either of the GNU General Public License Version 2 or later (the "GPL"),
28
* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
29
* in which case the provisions of the GPL or the LGPL are applicable instead
30
* of those above. If you wish to allow use of your version of this file only
31
* under the terms of either the GPL or the LGPL, and not to allow others to
32
* use your version of this file under the terms of the MPL, indicate your
33
* decision by deleting the provisions above and replace them with the notice
34
* and other provisions required by the GPL or the LGPL. If you do not delete
35
* the provisions above, a recipient may use your version of this file under
36
* the terms of any one of the MPL, the GPL or the LGPL.
38
* ***** END LICENSE BLOCK ***** */
40
/* @(#)s_tanh.c 1.3 95/01/18 */
42
* ====================================================
43
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
45
* Developed at SunSoft, a Sun Microsystems, Inc. business.
46
* Permission to use, copy, modify, and distribute this
47
* software is freely granted, provided that this notice
49
* ====================================================
53
* Return the Hyperbolic Tangent of x
58
* 0. tanh(x) is defined to be -----------
61
* 1. reduce x to non-negative by tanh(-x) = -tanh(x).
62
* 2. 0 <= x <= 2**-55 : tanh(x) := x*(one+x)
64
* 2**-55 < x <= 1 : tanh(x) := -----; t = expm1(-2x)
67
* 1 <= x <= 22.0 : tanh(x) := 1- ----- ; t=expm1(2x)
69
* 22.0 < x <= INF : tanh(x) := 1.
73
* only tanh(0)=0 is exact for finite argument.
79
static const double one=1.0, two=2.0, tiny = 1.0e-300;
81
static double one=1.0, two=2.0, tiny = 1.0e-300;
85
double fd_tanh(double x)
95
/* High word of |x|. */
100
/* x is INF or NaN */
102
if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */
103
else return one/x-one; /* tanh(NaN) = NaN */
107
if (ix < 0x40360000) { /* |x|<22 */
108
if (ix<0x3c800000) /* |x|<2**-55 */
109
return x*(one+x); /* tanh(small) = small */
110
if (ix>=0x3ff00000) { /* |x|>=1 */
111
t = fd_expm1(two*fd_fabs(x));
112
z = one - two/(t+two);
114
t = fd_expm1(-two*fd_fabs(x));
117
/* |x| > 22, return +-1 */
119
z = one - tiny; /* raised inexact flag */
121
return (jx>=0)? z: -z;
added
removed
src/dom/js/fdlibm/s_tanh.c
