1 | head 1.4;
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2 | access;
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3 | symbols;
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4 | locks; strict;
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5 | comment @;;; @;
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6 |
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7 |
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8 | 1.4
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9 | date 2009.01.22.04.09.05; author marek; state Exp;
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10 | branches;
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11 | next 1.3;
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12 |
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13 | 1.3
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14 | date 2009.01.19.09.32.12; author marek; state Exp;
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15 | branches;
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16 | next 1.2;
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17 |
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18 | 1.2
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19 | date 2009.01.19.07.53.33; author marek; state Exp;
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20 | branches;
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21 | next 1.1;
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22 |
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23 | 1.1
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24 | date 2009.01.19.06.41.22; author marek; state Exp;
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25 | branches;
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26 | next ;
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27 |
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28 |
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29 | desc
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30 | @@
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31 |
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32 |
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33 | 1.4
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34 | log
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35 | @*** empty log message ***
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36 | @
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37 | text
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38 | @#|
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39 | $Id$
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40 | *--------------------------------------------------------------------------*
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41 | | Copyright (C) 1994, Marek Rychlik (e-mail: rychlik@@math.arizona.edu) |
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42 | | Department of Mathematics, University of Arizona, Tucson, AZ 85721 |
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43 | | |
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44 | | Everyone is permitted to copy, distribute and modify the code in this |
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45 | | directory, as long as this copyright note is preserved verbatim. |
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46 | *--------------------------------------------------------------------------*
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47 | |#
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48 |
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49 | (defpackage "XGCD"
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50 | (:use "COMMON-LISP")
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51 | (:export xgcd))
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52 | (in-package "XGCD")
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53 |
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54 | #+debug(proclaim '(optimize (speed 0) (debug 3)))
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55 | #-debug(proclaim '(optimize (speed 3) (debug 0)))
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56 |
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57 | (defun xgcd (X Y)
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58 | "Extended gcd; the call
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59 | (xgcd X Y)
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60 | returns a multiple value list:
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61 | - GCD
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62 | - U,V such that they solve the equation
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63 | GCD=U*X+V*Y
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64 | - U1,V1 such that
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65 | LCM=U1*X=V1*Y (up to the sign)."
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66 | (labels ((xgcd-aux (x0 x1 u0 v0 u1 v1)
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67 | (cond
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68 | ((= x1 0) (values x0 u0 v0 u1 v1))
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69 | (t (multiple-value-bind (n x2) (floor x0 x1)
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70 | (let ((u2 (- u0 (* n u1)))
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71 | (v2 (- v0 (* n v1))))
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72 | (xgcd-aux x1 x2 u1 v1 u2 v2)))))))
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73 | (xgcd-aux X Y 1 0 0 1)))
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74 |
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75 |
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76 | @
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77 |
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78 |
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79 | 1.3
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80 | log
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81 | @*** empty log message ***
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82 | @
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83 | text
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84 | @d17 2
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85 | a18 2
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86 | ;;(proclaim '(optimize (speed 0) (debug 3)))
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87 | (proclaim '(optimize (speed 3) (debug 0)))
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88 | @
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89 |
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90 |
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91 | 1.2
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92 | log
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93 | @*** empty log message ***
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94 | @
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95 | text
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96 | @d2 1
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97 | a2 1
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98 | $Id: xgcd.lisp,v 1.1 2009/01/19 06:41:22 marek Exp marek $
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99 | d17 2
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100 | a18 1
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101 | (proclaim '(optimize (speed 0) (debug 3)))
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102 | @
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103 |
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104 |
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105 | 1.1
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106 | log
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107 | @Initial revision
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108 | @
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109 | text
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110 | @d2 1
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111 | a2 1
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112 | $Id: xgcd.lisp,v 1.3 1997/12/07 05:51:11 marek Exp $
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113 | d17 2
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114 | @
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