1 | |
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2 | /* @(#)e_remainder.c 5.1 93/09/24 */ |
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3 | /* |
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4 | * ==================================================== |
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5 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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6 | * |
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7 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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8 | * Permission to use, copy, modify, and distribute this |
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9 | * software is freely granted, provided that this notice |
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10 | * is preserved. |
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11 | * ==================================================== |
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12 | */ |
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13 | |
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14 | /* |
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15 | FUNCTION |
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16 | <<remainder>>, <<remainderf>>---round and remainder |
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17 | INDEX |
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18 | remainder |
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19 | INDEX |
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20 | remainderf |
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21 | |
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22 | SYNOPSIS |
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23 | #include <math.h> |
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24 | double remainder(double <[x]>, double <[y]>); |
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25 | float remainderf(float <[x]>, float <[y]>); |
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26 | |
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27 | DESCRIPTION |
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28 | <<remainder>> and <<remainderf>> find the remainder of |
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29 | <[x]>/<[y]>; this value is in the range -<[y]>/2 .. +<[y]>/2. |
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30 | |
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31 | RETURNS |
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32 | <<remainder>> returns the integer result as a double. |
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33 | |
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34 | PORTABILITY |
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35 | <<remainder>> is a System V release 4. |
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36 | <<remainderf>> is an extension. |
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37 | |
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38 | */ |
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39 | |
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40 | /* remainder(x,p) |
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41 | * Return : |
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42 | * returns x REM p = x - [x/p]*p as if in infinite |
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43 | * precise arithmetic, where [x/p] is the (infinite bit) |
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44 | * integer nearest x/p (in half way case choose the even one). |
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45 | * Method : |
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46 | * Based on fmod() return x-[x/p]chopped*p exactlp. |
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47 | */ |
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48 | |
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49 | #include "fdlibm.h" |
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50 | |
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51 | #ifndef _DOUBLE_IS_32BITS |
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52 | |
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53 | #ifdef __STDC__ |
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54 | static const double zero = 0.0; |
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55 | #else |
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56 | static double zero = 0.0; |
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57 | #endif |
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58 | |
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59 | |
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60 | #ifdef __STDC__ |
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61 | double remainder(double x, double p) |
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62 | #else |
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63 | double remainder(x,p) |
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64 | double x,p; |
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65 | #endif |
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66 | { |
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67 | __int32_t hx,hp; |
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68 | __uint32_t sx,lx,lp; |
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69 | double p_half; |
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70 | |
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71 | EXTRACT_WORDS(hx,lx,x); |
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72 | EXTRACT_WORDS(hp,lp,p); |
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73 | sx = hx&0x80000000; |
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74 | hp &= 0x7fffffff; |
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75 | hx &= 0x7fffffff; |
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76 | |
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77 | /* purge off exception values */ |
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78 | if((hp|lp)==0) return (x*p)/(x*p); /* p = 0 */ |
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79 | if((hx>=0x7ff00000)|| /* x not finite */ |
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80 | ((hp>=0x7ff00000)&& /* p is NaN */ |
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81 | (((hp-0x7ff00000)|lp)!=0))) |
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82 | return (x*p)/(x*p); |
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83 | |
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84 | |
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85 | if (hp<=0x7fdfffff) x = fmod(x,p+p); /* now x < 2p */ |
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86 | if (((hx-hp)|(lx-lp))==0) return zero*x; |
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87 | x = fabs(x); |
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88 | p = fabs(p); |
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89 | if (hp<0x00200000) { |
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90 | if(x+x>p) { |
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91 | x-=p; |
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92 | if(x+x>=p) x -= p; |
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93 | } |
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94 | } else { |
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95 | p_half = 0.5*p; |
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96 | if(x>p_half) { |
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97 | x-=p; |
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98 | if(x>=p_half) x -= p; |
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99 | } |
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100 | } |
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101 | GET_HIGH_WORD(hx,x); |
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102 | SET_HIGH_WORD(x,hx^sx); |
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103 | return x; |
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104 | } |
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105 | |
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106 | #endif /* defined(_DOUBLE_IS_32BITS) */ |
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