1 | /* |
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2 | FUNCTION |
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3 | <<lldiv>>---divide two long long integers |
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4 | |
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5 | INDEX |
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6 | lldiv |
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7 | |
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8 | SYNOPSIS |
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9 | #include <stdlib.h> |
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10 | lldiv_t lldiv(long long <[n]>, long long <[d]>); |
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11 | |
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12 | DESCRIPTION |
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13 | Divide |
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14 | @tex |
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15 | $n/d$, |
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16 | @end tex |
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17 | @ifnottex |
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18 | <[n]>/<[d]>, |
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19 | @end ifnottex |
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20 | returning quotient and remainder as two long long integers in a structure |
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21 | <<lldiv_t>>. |
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22 | |
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23 | RETURNS |
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24 | The result is represented with the structure |
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25 | |
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26 | . typedef struct |
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27 | . { |
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28 | . long long quot; |
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29 | . long long rem; |
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30 | . } lldiv_t; |
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31 | |
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32 | where the <<quot>> field represents the quotient, and <<rem>> the |
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33 | remainder. For nonzero <[d]>, if `<<<[r]> = ldiv(<[n]>,<[d]>);>>' then |
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34 | <[n]> equals `<<<[r]>.rem + <[d]>*<[r]>.quot>>'. |
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35 | |
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36 | To divide <<long>> rather than <<long long>> values, use the similar |
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37 | function <<ldiv>>. |
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38 | |
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39 | PORTABILITY |
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40 | <<lldiv>> is ISO 9899 (C99) compatable. |
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41 | |
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42 | No supporting OS subroutines are required. |
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43 | */ |
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44 | |
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45 | /*- |
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46 | * Copyright (c) 2001 Mike Barcroft <mike@FreeBSD.org> |
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47 | * All rights reserved. |
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48 | * |
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49 | * Redistribution and use in source and binary forms, with or without |
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50 | * modification, are permitted provided that the following conditions |
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51 | * are met: |
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52 | * 1. Redistributions of source code must retain the above copyright |
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53 | * notice, this list of conditions and the following disclaimer. |
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54 | * 2. Redistributions in binary form must reproduce the above copyright |
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55 | * notice, this list of conditions and the following disclaimer in the |
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56 | * documentation and/or other materials provided with the distribution. |
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57 | * |
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58 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND |
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59 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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60 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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61 | * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
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62 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
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63 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
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64 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
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65 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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66 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
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67 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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68 | * SUCH DAMAGE. |
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69 | */ |
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70 | |
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71 | #include <stdlib.h> |
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72 | |
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73 | /* |
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74 | * The ANSI standard says that |r.quot| <= |n/d|, where |
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75 | * n/d is to be computed in infinite precision. In other |
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76 | * words, we should always truncate the quotient towards |
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77 | * 0, never -infinity. |
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78 | * |
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79 | * Machine division and remainer may work either way when |
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80 | * one or both of n or d is negative. If only one is |
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81 | * negative and r.quot has been truncated towards -inf, |
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82 | * r.rem will have the same sign as denom and the opposite |
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83 | * sign of num; if both are negative and r.quot has been |
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84 | * truncated towards -inf, r.rem will be positive (will |
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85 | * have the opposite sign of num). These are considered |
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86 | * `wrong'. |
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87 | * |
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88 | * If both are num and denom are positive, r will always |
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89 | * be positive. |
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90 | * |
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91 | * This all boils down to: |
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92 | * if num >= 0, but r.rem < 0, we got the wrong answer. |
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93 | * In that case, to get the right answer, add 1 to r.quot and |
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94 | * subtract denom from r.rem. |
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95 | */ |
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96 | lldiv_t |
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97 | lldiv (long long numer, long long denom) |
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98 | { |
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99 | lldiv_t retval; |
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100 | |
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101 | retval.quot = numer / denom; |
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102 | retval.rem = numer % denom; |
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103 | if (numer >= 0 && retval.rem < 0) { |
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104 | retval.quot++; |
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105 | retval.rem -= denom; |
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106 | } |
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107 | return (retval); |
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108 | } |
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109 | |
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