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1 function [g, v] = gcd (a, ...) |
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2 |
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3 # [g [, v]] = gcd (a) returns the greatest common divisor g of the |
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4 # entries of the integer vector a, and an integer vector v such that |
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5 # g = v(1) * a(k) + ... + v(k) * a(k). |
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6 # |
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7 # [g [, v]] = gcd (a1, ..., ak) is the same with a = [a1, ..., ak]. |
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8 |
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9 # Written by KH (Kurt.Hornik@ci.tuwien.ac.at) on Sep 16, 1994 |
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10 # Copyright Dept of Statistics and Probability Theory TU Wien |
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11 |
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12 if (nargin > 1) |
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13 va_start; |
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14 for k=2:nargin; |
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15 a = [a, va_arg()]; |
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16 endfor |
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17 endif |
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18 |
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19 if (round(a) != a) |
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20 error("gcd: all arguments must be integer"); |
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21 endif |
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22 |
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23 g = abs(a(1)); |
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24 v = sign(a(1)); |
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25 for k=1:(length(a)-1) |
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26 x = [g, 1, 0]; |
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27 y = [abs(a(k+1)), 0, 1]; |
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28 while (y(1) > 0) |
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29 r = x - y * floor(x(1) / y(1)); |
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30 x = y; |
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31 y = r; |
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32 endwhile |
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33 g = x(1); |
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34 v = [x(2) * v, x(3) * sign(a(k+1))]; |
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35 endfor |
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36 |
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37 endfunction |
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38 |
