1 | |
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2 | /* @(#)s_modf.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 | <<modf>>, <<modff>>---split fractional and integer parts |
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17 | |
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18 | INDEX |
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19 | modf |
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20 | INDEX |
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21 | modff |
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22 | |
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23 | SYNOPSIS |
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24 | #include <math.h> |
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25 | double modf(double <[val]>, double *<[ipart]>); |
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26 | float modff(float <[val]>, float *<[ipart]>); |
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27 | |
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28 | DESCRIPTION |
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29 | <<modf>> splits the double <[val]> apart into an integer part |
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30 | and a fractional part, returning the fractional part and |
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31 | storing the integer part in <<*<[ipart]>>>. No rounding |
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32 | whatsoever is done; the sum of the integer and fractional |
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33 | parts is guaranteed to be exactly equal to <[val]>. That |
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34 | is, if <[realpart]> = modf(<[val]>, &<[intpart]>); then |
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35 | `<<<[realpart]>+<[intpart]>>>' is the same as <[val]>. |
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36 | <<modff>> is identical, save that it takes and returns |
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37 | <<float>> rather than <<double>> values. |
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38 | |
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39 | RETURNS |
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40 | The fractional part is returned. Each result has the same |
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41 | sign as the supplied argument <[val]>. |
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42 | |
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43 | PORTABILITY |
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44 | <<modf>> is ANSI C. <<modff>> is an extension. |
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45 | |
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46 | QUICKREF |
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47 | modf ansi pure |
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48 | modff - pure |
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49 | |
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50 | */ |
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51 | |
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52 | /* |
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53 | * modf(double x, double *iptr) |
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54 | * return fraction part of x, and return x's integral part in *iptr. |
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55 | * Method: |
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56 | * Bit twiddling. |
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57 | * |
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58 | * Exception: |
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59 | * No exception. |
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60 | */ |
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61 | |
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62 | #include "fdlibm.h" |
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63 | |
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64 | #ifndef _DOUBLE_IS_32BITS |
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65 | |
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66 | #ifdef __STDC__ |
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67 | static const double one = 1.0; |
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68 | #else |
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69 | static double one = 1.0; |
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70 | #endif |
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71 | |
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72 | #ifdef __STDC__ |
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73 | double modf(double x, double *iptr) |
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74 | #else |
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75 | double modf(x, iptr) |
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76 | double x,*iptr; |
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77 | #endif |
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78 | { |
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79 | __int32_t i0,i1,j0; |
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80 | __uint32_t i; |
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81 | EXTRACT_WORDS(i0,i1,x); |
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82 | j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */ |
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83 | if(j0<20) { /* integer part in high x */ |
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84 | if(j0<0) { /* |x|<1 */ |
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85 | INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */ |
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86 | return x; |
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87 | } else { |
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88 | i = (0x000fffff)>>j0; |
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89 | if(((i0&i)|i1)==0) { /* x is integral */ |
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90 | __uint32_t high; |
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91 | *iptr = x; |
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92 | GET_HIGH_WORD(high,x); |
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93 | INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ |
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94 | return x; |
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95 | } else { |
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96 | INSERT_WORDS(*iptr,i0&(~i),0); |
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97 | return x - *iptr; |
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98 | } |
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99 | } |
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100 | } else if (j0>51) { /* no fraction part */ |
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101 | __uint32_t high; |
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102 | *iptr = x*one; |
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103 | GET_HIGH_WORD(high,x); |
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104 | INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ |
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105 | return x; |
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106 | } else { /* fraction part in low x */ |
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107 | i = ((__uint32_t)(0xffffffff))>>(j0-20); |
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108 | if((i1&i)==0) { /* x is integral */ |
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109 | __uint32_t high; |
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110 | *iptr = x; |
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111 | GET_HIGH_WORD(high,x); |
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112 | INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ |
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113 | return x; |
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114 | } else { |
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115 | INSERT_WORDS(*iptr,i0,i1&(~i)); |
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116 | return x - *iptr; |
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117 | } |
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118 | } |
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119 | } |
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120 | |
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121 | #endif /* _DOUBLE_IS_32BITS */ |
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