/[jscoverage]/trunk/js/src/fdlibm/e_cosh.c
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Annotation of /trunk/js/src/fdlibm/e_cosh.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_cosh.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     /* __ieee754_cosh(x)
53     * Method :
54     * mathematically cosh(x) if defined to be (exp(x)+exp(-x))/2
55     * 1. Replace x by |x| (cosh(x) = cosh(-x)).
56     * 2.
57     * [ exp(x) - 1 ]^2
58     * 0 <= x <= ln2/2 : cosh(x) := 1 + -------------------
59     * 2*exp(x)
60     *
61     * exp(x) + 1/exp(x)
62     * ln2/2 <= x <= 22 : cosh(x) := -------------------
63     * 2
64     * 22 <= x <= lnovft : cosh(x) := exp(x)/2
65     * lnovft <= x <= ln2ovft: cosh(x) := exp(x/2)/2 * exp(x/2)
66     * ln2ovft < x : cosh(x) := huge*huge (overflow)
67     *
68     * Special cases:
69     * cosh(x) is |x| if x is +INF, -INF, or NaN.
70     * only cosh(0)=1 is exact for finite x.
71     */
72    
73     #include "fdlibm.h"
74    
75     #ifdef _WIN32
76     #define huge myhuge
77     #endif
78    
79     #ifdef __STDC__
80     static const double one = 1.0, half=0.5, really_big = 1.0e300;
81     #else
82     static double one = 1.0, half=0.5, really_big = 1.0e300;
83     #endif
84    
85     #ifdef __STDC__
86     double __ieee754_cosh(double x)
87     #else
88     double __ieee754_cosh(x)
89     double x;
90     #endif
91     {
92     fd_twoints u;
93     double t,w;
94     int ix;
95     unsigned lx;
96    
97     /* High word of |x|. */
98     u.d = x;
99     ix = __HI(u);
100     ix &= 0x7fffffff;
101    
102     /* x is INF or NaN */
103     if(ix>=0x7ff00000) return x*x;
104    
105     /* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
106     if(ix<0x3fd62e43) {
107     t = fd_expm1(fd_fabs(x));
108     w = one+t;
109     if (ix<0x3c800000) return w; /* cosh(tiny) = 1 */
110     return one+(t*t)/(w+w);
111     }
112    
113     /* |x| in [0.5*ln2,22], return (exp(|x|)+1/exp(|x|)/2; */
114     if (ix < 0x40360000) {
115     t = __ieee754_exp(fd_fabs(x));
116     return half*t+half/t;
117     }
118    
119     /* |x| in [22, log(maxdouble)] return half*exp(|x|) */
120     if (ix < 0x40862E42) return half*__ieee754_exp(fd_fabs(x));
121    
122     /* |x| in [log(maxdouble), overflowthresold] */
123     lx = *( (((*(unsigned*)&one)>>29)) + (unsigned*)&x);
124     if (ix<0x408633CE ||
125     (ix==0x408633ce)&&(lx<=(unsigned)0x8fb9f87d)) {
126     w = __ieee754_exp(half*fd_fabs(x));
127     t = half*w;
128     return t*w;
129     }
130    
131     /* |x| > overflowthresold, cosh(x) overflow */
132     return really_big*really_big;
133     }

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