/[jscoverage]/trunk/js/src/fdlibm/e_atanh.c
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Contents of /trunk/js/src/fdlibm/e_atanh.c

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Wed Aug 1 13:51:53 2007 UTC (12 years, 10 months ago) by siliconforks
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Initial import.

1 /* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
2 *
3 * ***** BEGIN LICENSE BLOCK *****
4 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
5 *
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/
10 *
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
14 * License.
15 *
16 * The Original Code is Mozilla Communicator client code, released
17 * March 31, 1998.
18 *
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.
23 *
24 * Contributor(s):
25 *
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.
37 *
38 * ***** END LICENSE BLOCK ***** */
39
40 /* @(#)e_atanh.c 1.3 95/01/18 */
41 /*
42 * ====================================================
43 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
44 *
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
48 * is preserved.
49 * ====================================================
50 *
51 */
52
53 /* __ieee754_atanh(x)
54 * Method :
55 * 1.Reduced x to positive by atanh(-x) = -atanh(x)
56 * 2.For x>=0.5
57 * 1 2x x
58 * atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
59 * 2 1 - x 1 - x
60 *
61 * For x<0.5
62 * atanh(x) = 0.5*log1p(2x+2x*x/(1-x))
63 *
64 * Special cases:
65 * atanh(x) is NaN if |x| > 1 with signal;
66 * atanh(NaN) is that NaN with no signal;
67 * atanh(+-1) is +-INF with signal.
68 *
69 */
70
71 #include "fdlibm.h"
72
73 #ifdef __STDC__
74 static const double one = 1.0, really_big = 1e300;
75 #else
76 static double one = 1.0, really_big = 1e300;
77 #endif
78
79 static double zero = 0.0;
80
81 #ifdef __STDC__
82 double __ieee754_atanh(double x)
83 #else
84 double __ieee754_atanh(x)
85 double x;
86 #endif
87 {
88 double t;
89 int hx,ix;
90 unsigned lx;
91 fd_twoints u;
92 u.d = x;
93 hx = __HI(u); /* high word */
94 lx = __LO(u); /* low word */
95 ix = hx&0x7fffffff;
96 if ((ix|((lx|(-(int)lx))>>31))>0x3ff00000) /* |x|>1 */
97 return (x-x)/(x-x);
98 if(ix==0x3ff00000)
99 return x/zero;
100 if(ix<0x3e300000&&(really_big+x)>zero) return x; /* x<2**-28 */
101 u.d = x;
102 __HI(u) = ix; /* x <- |x| */
103 x = u.d;
104 if(ix<0x3fe00000) { /* x < 0.5 */
105 t = x+x;
106 t = 0.5*fd_log1p(t+t*x/(one-x));
107 } else
108 t = 0.5*fd_log1p((x+x)/(one-x));
109 if(hx>=0) return t; else return -t;
110 }

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