/[jscoverage]/trunk/js/src/fdlibm/s_cos.c
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Annotation of /trunk/js/src/fdlibm/s_cos.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     /* @(#)s_cos.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     /* cos(x)
53     * Return cosine function of x.
54     *
55     * kernel function:
56     * __kernel_sin ... sine function on [-pi/4,pi/4]
57     * __kernel_cos ... cosine function on [-pi/4,pi/4]
58     * __ieee754_rem_pio2 ... argument reduction routine
59     *
60     * Method.
61     * Let S,C and T denote the sin, cos and tan respectively on
62     * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
63     * in [-pi/4 , +pi/4], and let n = k mod 4.
64     * We have
65     *
66     * n sin(x) cos(x) tan(x)
67     * ----------------------------------------------------------
68     * 0 S C T
69     * 1 C -S -1/T
70     * 2 -S -C T
71     * 3 -C S -1/T
72     * ----------------------------------------------------------
73     *
74     * Special cases:
75     * Let trig be any of sin, cos, or tan.
76     * trig(+-INF) is NaN, with signals;
77     * trig(NaN) is that NaN;
78     *
79     * Accuracy:
80     * TRIG(x) returns trig(x) nearly rounded
81     */
82    
83     #include "fdlibm.h"
84    
85     #ifdef __STDC__
86     double fd_cos(double x)
87     #else
88     double fd_cos(x)
89     double x;
90     #endif
91     {
92     fd_twoints u;
93     double y[2],z=0.0;
94     int n, ix;
95    
96     /* High word of x. */
97     u.d = x;
98     ix = __HI(u);
99    
100     /* |x| ~< pi/4 */
101     ix &= 0x7fffffff;
102     if(ix <= 0x3fe921fb) return __kernel_cos(x,z);
103    
104     /* cos(Inf or NaN) is NaN */
105     else if (ix>=0x7ff00000) return x-x;
106    
107     /* argument reduction needed */
108     else {
109     n = __ieee754_rem_pio2(x,y);
110     switch(n&3) {
111     case 0: return __kernel_cos(y[0],y[1]);
112     case 1: return -__kernel_sin(y[0],y[1],1);
113     case 2: return -__kernel_cos(y[0],y[1]);
114     default:
115     return __kernel_sin(y[0],y[1],1);
116     }
117     }
118     }

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