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

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Revision 2 - (show annotations)
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_acosh.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_acosh(x)
54 * Method :
55 * Based on
56 * acosh(x) = log [ x + sqrt(x*x-1) ]
57 * we have
58 * acosh(x) := log(x)+ln2, if x is large; else
59 * acosh(x) := log(2x-1/(sqrt(x*x-1)+x)) if x>2; else
60 * acosh(x) := log1p(t+sqrt(2.0*t+t*t)); where t=x-1.
61 *
62 * Special cases:
63 * acosh(x) is NaN with signal if x<1.
64 * acosh(NaN) is NaN without signal.
65 */
66
67 #include "fdlibm.h"
68
69 #ifdef __STDC__
70 static const double
71 #else
72 static double
73 #endif
74 one = 1.0,
75 ln2 = 6.93147180559945286227e-01; /* 0x3FE62E42, 0xFEFA39EF */
76
77 #ifdef __STDC__
78 double __ieee754_acosh(double x)
79 #else
80 double __ieee754_acosh(x)
81 double x;
82 #endif
83 {
84 fd_twoints u;
85 double t;
86 int hx;
87 u.d = x;
88 hx = __HI(u);
89 if(hx<0x3ff00000) { /* x < 1 */
90 return (x-x)/(x-x);
91 } else if(hx >=0x41b00000) { /* x > 2**28 */
92 if(hx >=0x7ff00000) { /* x is inf of NaN */
93 return x+x;
94 } else
95 return __ieee754_log(x)+ln2; /* acosh(huge)=log(2x) */
96 } else if(((hx-0x3ff00000)|__LO(u))==0) {
97 return 0.0; /* acosh(1) = 0 */
98 } else if (hx > 0x40000000) { /* 2**28 > x > 2 */
99 t=x*x;
100 return __ieee754_log(2.0*x-one/(x+fd_sqrt(t-one)));
101 } else { /* 1<x<2 */
102 t = x-one;
103 return fd_log1p(t+fd_sqrt(2.0*t+t*t));
104 }
105 }

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