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annotate src/libm/s_cos.c @ 2763:6fc50bdd88c0

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Some cleanups on the new XInput code. One or two things got moved around, but largely this is hooked up correctly in the Unix configure system now: it can be dynamically loaded and fallback gracefully if not available, or libXi can be directly linked to libSDL. XInput support can be --disable'd from the configure script, too (defaults to enabled). Please note that while the framework is in place to gracefully fallback, the current state of the source requires XInput. We'll need to adjust a few things still to correct this.
author Ryan C. Gordon <icculus@icculus.org>
date Wed, 17 Sep 2008 08:20:57 +0000
parents a98604b691c8
children dc1eb82ffdaa
rev   line source
2756
a98604b691c8 Expanded the libm support and put it into a separate directory.
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1 /* @(#)s_cos.c 5.1 93/09/24 */
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2 /*
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3 * ====================================================
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4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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5 *
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6 * Developed at SunPro, a Sun Microsystems, Inc. business.
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7 * Permission to use, copy, modify, and distribute this
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8 * software is freely granted, provided that this notice
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9 * is preserved.
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10 * ====================================================
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11 */
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12
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13 #if defined(LIBM_SCCS) && !defined(lint)
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14 static char rcsid[] = "$NetBSD: s_cos.c,v 1.7 1995/05/10 20:47:02 jtc Exp $";
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15 #endif
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16
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17 /* cos(x)
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18 * Return cosine function of x.
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19 *
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20 * kernel function:
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21 * __kernel_sin ... sine function on [-pi/4,pi/4]
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22 * __kernel_cos ... cosine function on [-pi/4,pi/4]
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23 * __ieee754_rem_pio2 ... argument reduction routine
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24 *
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25 * Method.
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26 * Let S,C and T denote the sin, cos and tan respectively on
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27 * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
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28 * in [-pi/4 , +pi/4], and let n = k mod 4.
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29 * We have
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30 *
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31 * n sin(x) cos(x) tan(x)
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32 * ----------------------------------------------------------
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33 * 0 S C T
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34 * 1 C -S -1/T
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35 * 2 -S -C T
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36 * 3 -C S -1/T
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37 * ----------------------------------------------------------
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38 *
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39 * Special cases:
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40 * Let trig be any of sin, cos, or tan.
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41 * trig(+-INF) is NaN, with signals;
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42 * trig(NaN) is that NaN;
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43 *
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44 * Accuracy:
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45 * TRIG(x) returns trig(x) nearly rounded
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46 */
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47
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48 #include "math.h"
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49 #include "math_private.h"
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50
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51 libm_hidden_proto(cos)
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52 #ifdef __STDC__
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53 double cos(double x)
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54 #else
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55 double cos(x)
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56 double x;
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57 #endif
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58 {
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59 double y[2], z = 0.0;
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60 int32_t n, ix;
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61
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62 /* High word of x. */
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63 GET_HIGH_WORD(ix, x);
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64
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65 /* |x| ~< pi/4 */
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66 ix &= 0x7fffffff;
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67 if (ix <= 0x3fe921fb)
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68 return __kernel_cos(x, z);
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69
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70 /* cos(Inf or NaN) is NaN */
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71 else if (ix >= 0x7ff00000)
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72 return x - x;
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73
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74 /* argument reduction needed */
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75 else {
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76 n = __ieee754_rem_pio2(x, y);
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77 switch (n & 3) {
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78 case 0:
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79 return __kernel_cos(y[0], y[1]);
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80 case 1:
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81 return -__kernel_sin(y[0], y[1], 1);
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82 case 2:
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83 return -__kernel_cos(y[0], y[1]);
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84 default:
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85 return __kernel_sin(y[0], y[1], 1);
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86 }
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87 }
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88 }
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89
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90 libm_hidden_def(cos)