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

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Wed Aug 1 13:51:53 2007 UTC (14 years, 11 months ago) by siliconforks
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Initial import.

1 siliconforks 2 /* -*- 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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