mirror of
https://github.com/signalwire/freeswitch.git
synced 2025-04-04 04:05:15 +00:00
fff98f6316
git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@3693 d0543943-73ff-0310-b7d9-9358b9ac24b2
123 lines
3.8 KiB
C
123 lines
3.8 KiB
C
/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
|
|
*
|
|
* ***** BEGIN LICENSE BLOCK *****
|
|
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
|
|
*
|
|
* The contents of this file are subject to the Mozilla Public License Version
|
|
* 1.1 (the "License"); you may not use this file except in compliance with
|
|
* the License. You may obtain a copy of the License at
|
|
* http://www.mozilla.org/MPL/
|
|
*
|
|
* Software distributed under the License is distributed on an "AS IS" basis,
|
|
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
|
|
* for the specific language governing rights and limitations under the
|
|
* License.
|
|
*
|
|
* The Original Code is Mozilla Communicator client code, released
|
|
* March 31, 1998.
|
|
*
|
|
* The Initial Developer of the Original Code is
|
|
* Sun Microsystems, Inc.
|
|
* Portions created by the Initial Developer are Copyright (C) 1998
|
|
* the Initial Developer. All Rights Reserved.
|
|
*
|
|
* Contributor(s):
|
|
*
|
|
* Alternatively, the contents of this file may be used under the terms of
|
|
* either of the GNU General Public License Version 2 or later (the "GPL"),
|
|
* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
|
|
* in which case the provisions of the GPL or the LGPL are applicable instead
|
|
* of those above. If you wish to allow use of your version of this file only
|
|
* under the terms of either the GPL or the LGPL, and not to allow others to
|
|
* use your version of this file under the terms of the MPL, indicate your
|
|
* decision by deleting the provisions above and replace them with the notice
|
|
* and other provisions required by the GPL or the LGPL. If you do not delete
|
|
* the provisions above, a recipient may use your version of this file under
|
|
* the terms of any one of the MPL, the GPL or the LGPL.
|
|
*
|
|
* ***** END LICENSE BLOCK ***** */
|
|
|
|
/* @(#)s_tanh.c 1.3 95/01/18 */
|
|
/*
|
|
* ====================================================
|
|
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
|
|
*
|
|
* Developed at SunSoft, a Sun Microsystems, Inc. business.
|
|
* Permission to use, copy, modify, and distribute this
|
|
* software is freely granted, provided that this notice
|
|
* is preserved.
|
|
* ====================================================
|
|
*/
|
|
|
|
/* Tanh(x)
|
|
* Return the Hyperbolic Tangent of x
|
|
*
|
|
* Method :
|
|
* x -x
|
|
* e - e
|
|
* 0. tanh(x) is defined to be -----------
|
|
* x -x
|
|
* e + e
|
|
* 1. reduce x to non-negative by tanh(-x) = -tanh(x).
|
|
* 2. 0 <= x <= 2**-55 : tanh(x) := x*(one+x)
|
|
* -t
|
|
* 2**-55 < x <= 1 : tanh(x) := -----; t = expm1(-2x)
|
|
* t + 2
|
|
* 2
|
|
* 1 <= x <= 22.0 : tanh(x) := 1- ----- ; t=expm1(2x)
|
|
* t + 2
|
|
* 22.0 < x <= INF : tanh(x) := 1.
|
|
*
|
|
* Special cases:
|
|
* tanh(NaN) is NaN;
|
|
* only tanh(0)=0 is exact for finite argument.
|
|
*/
|
|
|
|
#include "fdlibm.h"
|
|
|
|
#ifdef __STDC__
|
|
static const double one=1.0, two=2.0, tiny = 1.0e-300;
|
|
#else
|
|
static double one=1.0, two=2.0, tiny = 1.0e-300;
|
|
#endif
|
|
|
|
#ifdef __STDC__
|
|
double fd_tanh(double x)
|
|
#else
|
|
double fd_tanh(x)
|
|
double x;
|
|
#endif
|
|
{
|
|
double t,z;
|
|
int jx,ix;
|
|
fd_twoints u;
|
|
|
|
/* High word of |x|. */
|
|
u.d = x;
|
|
jx = __HI(u);
|
|
ix = jx&0x7fffffff;
|
|
|
|
/* x is INF or NaN */
|
|
if(ix>=0x7ff00000) {
|
|
if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */
|
|
else return one/x-one; /* tanh(NaN) = NaN */
|
|
}
|
|
|
|
/* |x| < 22 */
|
|
if (ix < 0x40360000) { /* |x|<22 */
|
|
if (ix<0x3c800000) /* |x|<2**-55 */
|
|
return x*(one+x); /* tanh(small) = small */
|
|
if (ix>=0x3ff00000) { /* |x|>=1 */
|
|
t = fd_expm1(two*fd_fabs(x));
|
|
z = one - two/(t+two);
|
|
} else {
|
|
t = fd_expm1(-two*fd_fabs(x));
|
|
z= -t/(t+two);
|
|
}
|
|
/* |x| > 22, return +-1 */
|
|
} else {
|
|
z = one - tiny; /* raised inexact flag */
|
|
}
|
|
return (jx>=0)? z: -z;
|
|
}
|