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annotate lib/cosl.c @ 8563:c3d334708928

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Better support of signalling NaNs.
author Bruno Haible <bruno@clisp.org>
date Mon, 26 Mar 2007 22:26:05 +0000
parents c115624bf99a
children 678640901735
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1 /* s_cosl.c -- long double version of s_sin.c.
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2 * Conversion to long double by Jakub Jelinek, jj@ultra.linux.cz.
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3 */
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4
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5 /*
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6 * ====================================================
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7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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8 *
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9 * Developed at SunPro, a Sun Microsystems, Inc. business.
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10 * Permission to use, copy, modify, and distribute this
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11 * software is freely granted, provided that this notice
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12 * is preserved.
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13 * ====================================================
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14 */
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15
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16 #include <config.h>
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17
c115624bf99a New module 'math'. <math.h> replaces mathl.h.
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18 /* Specification. */
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19 #include <math.h>
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20
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21 /* sinl(x)
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22 * Return sine function of x.
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23 *
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24 * kernel function:
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25 * __kernel_sinl ... sine function on [-pi/4,pi/4]
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26 * __kernel_cosl ... cose function on [-pi/4,pi/4]
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27 * __ieee754_rem_pio2l ... argument reduction routine
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28 *
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29 * Method.
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30 * Let S,C and T denote the sin, cos and tan respectively on
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31 * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
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32 * in [-pi/4 , +pi/4], and let n = k mod 4.
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33 * We have
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34 *
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35 * n sin(x) cos(x) tan(x)
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36 * ----------------------------------------------------------
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37 * 0 S C T
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38 * 1 C -S -1/T
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39 * 2 -S -C T
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40 * 3 -C S -1/T
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41 * ----------------------------------------------------------
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42 *
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43 * Special cases:
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44 * Let trig be any of sin, cos, or tan.
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45 * trig(+-INF) is NaN, with signals;
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46 * trig(NaN) is that NaN;
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47 *
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48 * Accuracy:
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49 * TRIG(x) returns trig(x) nearly rounded
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50 */
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51
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52 #include "trigl.h"
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53 #ifdef HAVE_SINL
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54 #include "trigl.c"
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55 #include "sincosl.c"
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56 #endif
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57 #include "isnanl.h"
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58
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59 long double cosl(long double x)
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60 {
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61 long double y[2],z=0.0L;
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62 int n;
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63
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64 /* cosl(NaN) is NaN */
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65 if (isnanl (x))
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66 return x;
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67
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68 /* |x| ~< pi/4 */
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69 if(x >= -0.7853981633974483096156608458198757210492 &&
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70 x <= 0.7853981633974483096156608458198757210492)
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71 return kernel_cosl(x, z);
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72
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73 /* cosl(Inf) is NaN, cosl(0) is 1 */
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74 else if (x + x == x && x != 0.0)
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75 return x-x; /* NaN */
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76
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77 /* argument reduction needed */
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78 else {
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79 n = ieee754_rem_pio2l(x,y);
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80 switch(n&3) {
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81 case 0: return kernel_cosl(y[0],y[1]);
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82 case 1: return -kernel_sinl(y[0],y[1],1);
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83 case 2: return -kernel_cosl(y[0],y[1]);
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84 default:
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85 return kernel_sinl(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 #if 0
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91 int
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92 main (void)
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93 {
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94 printf ("%.16Lg\n", cosl(0.7853981633974483096156608458198757210492));
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95 printf ("%.16Lg\n", cosl(0.7853981633974483096156608458198757210492 *29));
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96 printf ("%.16Lg\n", cosl(0.7853981633974483096156608458198757210492 *2));
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97 printf ("%.16Lg\n", cosl(0.7853981633974483096156608458198757210492 *30));
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98 printf ("%.16Lg\n", cosl(0.7853981633974483096156608458198757210492 *4));
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99 printf ("%.16Lg\n", cosl(0.7853981633974483096156608458198757210492 *32));
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100 printf ("%.16Lg\n", cosl(0.7853981633974483096156608458198757210492 *2/3));
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101 printf ("%.16Lg\n", cosl(0.7853981633974483096156608458198757210492 *4/3));
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102 }
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103 #endif