Mercurial > sdl-ios-xcode

comparison src/libm/s_sin.c @ 2756:a98604b691c8

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Expanded the libm support and put it into a separate directory.
author Sam Lantinga <slouken@libsdl.org>
date Mon, 15 Sep 2008 06:33:23 +0000
parents
children dc1eb82ffdaa
comparison
equal deleted inserted replaced
2755:2a3ec308d995 2756:a98604b691c8
1 /* @(#)s_sin.c 5.1 93/09/24 */
2 /*
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 *
6 * Developed at SunPro, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
9 * is preserved.
10 * ====================================================
11 */
12
13 #if defined(LIBM_SCCS) && !defined(lint)
14 static char rcsid[] = "$NetBSD: s_sin.c,v 1.7 1995/05/10 20:48:15 jtc Exp $";
15 #endif
16
17 /* sin(x)
18 * Return sine function of x.
19 *
20 * kernel function:
21 * __kernel_sin ... sine function on [-pi/4,pi/4]
22 * __kernel_cos ... cose function on [-pi/4,pi/4]
23 * __ieee754_rem_pio2 ... argument reduction routine
24 *
25 * Method.
26 * Let S,C and T denote the sin, cos and tan respectively on
27 * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
28 * in [-pi/4 , +pi/4], and let n = k mod 4.
29 * We have
30 *
31 * n sin(x) cos(x) tan(x)
32 * ----------------------------------------------------------
33 * 0 S C T
34 * 1 C -S -1/T
35 * 2 -S -C T
36 * 3 -C S -1/T
37 * ----------------------------------------------------------
38 *
39 * Special cases:
40 * Let trig be any of sin, cos, or tan.
41 * trig(+-INF) is NaN, with signals;
42 * trig(NaN) is that NaN;
43 *
44 * Accuracy:
45 * TRIG(x) returns trig(x) nearly rounded
46 */
47
48 #include "math.h"
49 #include "math_private.h"
50
51 libm_hidden_proto(sin)
52 #ifdef __STDC__
53 double sin(double x)
54 #else
55 double sin(x)
56 double x;
57 #endif
58 {
59 double y[2], z = 0.0;
60 int32_t n, ix;
61
62 /* High word of x. */
63 GET_HIGH_WORD(ix, x);
64
65 /* |x| ~< pi/4 */
66 ix &= 0x7fffffff;
67 if (ix <= 0x3fe921fb)
68 return __kernel_sin(x, z, 0);
69
70 /* sin(Inf or NaN) is NaN */
71 else if (ix >= 0x7ff00000)
72 return x - x;
73
74 /* argument reduction needed */
75 else {
76 n = __ieee754_rem_pio2(x, y);
77 switch (n & 3) {
78 case 0:
79 return __kernel_sin(y[0], y[1], 1);
80 case 1:
81 return __kernel_cos(y[0], y[1]);
82 case 2:
83 return -__kernel_sin(y[0], y[1], 1);
84 default:
85 return -__kernel_cos(y[0], y[1]);
86 }
87 }
88 }
89
90 libm_hidden_def(sin)