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Contents of /trunk/js/src/fdlibm/s_asinh.c

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Revision 2 - (show annotations)
Wed Aug 1 13:51:53 2007 UTC (14 years, 9 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 /* @(#)s_asinh.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 /* asinh(x)
53 * Method :
54 * Based on
55 * asinh(x) = sign(x) * log [ |x| + sqrt(x*x+1) ]
56 * we have
57 * asinh(x) := x if 1+x*x=1,
58 * := sign(x)*(log(x)+ln2)) for large |x|, else
59 * := sign(x)*log(2|x|+1/(|x|+sqrt(x*x+1))) if|x|>2, else
60 * := sign(x)*log1p(|x| + x^2/(1 + sqrt(1+x^2)))
61 */
62
63 #include "fdlibm.h"
64
65 #ifdef __STDC__
66 static const double
67 #else
68 static double
69 #endif
70 one = 1.00000000000000000000e+00, /* 0x3FF00000, 0x00000000 */
71 ln2 = 6.93147180559945286227e-01, /* 0x3FE62E42, 0xFEFA39EF */
72 really_big= 1.00000000000000000000e+300;
73
74 #ifdef __STDC__
75 double fd_asinh(double x)
76 #else
77 double fd_asinh(x)
78 double x;
79 #endif
80 {
81 fd_twoints u;
82 double t,w;
83 int hx,ix;
84 u.d = x;
85 hx = __HI(u);
86 ix = hx&0x7fffffff;
87 if(ix>=0x7ff00000) return x+x; /* x is inf or NaN */
88 if(ix< 0x3e300000) { /* |x|<2**-28 */
89 if(really_big+x>one) return x; /* return x inexact except 0 */
90 }
91 if(ix>0x41b00000) { /* |x| > 2**28 */
92 w = __ieee754_log(fd_fabs(x))+ln2;
93 } else if (ix>0x40000000) { /* 2**28 > |x| > 2.0 */
94 t = fd_fabs(x);
95 w = __ieee754_log(2.0*t+one/(fd_sqrt(x*x+one)+t));
96 } else { /* 2.0 > |x| > 2**-28 */
97 t = x*x;
98 w =fd_log1p(fd_fabs(x)+t/(one+fd_sqrt(one+t)));
99 }
100 if(hx>0) return w; else return -w;
101 }

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