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1 ## Copyright (C) 1998 Auburn University. All rights reserved. |
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2 ## |
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3 ## This file is part of Octave. |
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4 ## |
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5 ## Octave is free software; you can redistribute it and/or modify it |
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6 ## under the terms of the GNU General Public License as published by |
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7 ## the Free Software Foundation; either version 2, or (at your option) |
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8 ## any later version. |
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9 ## |
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10 ## Octave is distributed in the hope that it will be useful, but |
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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13 ## General Public License for more details. |
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14 ## |
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15 ## You should have received a copy of the GNU General Public License |
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16 ## along with Octave; see the file COPYING. If not, write to the Free |
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17 ## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
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18 ## 02110-1301, USA. |
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19 |
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20 ## -*- texinfo -*- |
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21 ## @deftypefn {Function File} {} qmult (@var{a}, @var{b}) |
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22 ## Multiply two quaternions. |
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23 ## |
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24 ## @example |
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25 ## [w, x, y, z] = w*i + x*j + y*k + z |
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26 ## @end example |
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27 ## |
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28 ## @noindent |
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29 ## identities: |
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30 ## |
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31 ## @example |
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32 ## i^2 = j^2 = k^2 = -1 |
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33 ## ij = k jk = i |
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34 ## ki = j kj = -i |
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35 ## ji = -k ik = -j |
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36 ## @end example |
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37 ## @end deftypefn |
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38 |
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39 ## Author: A. S. Hodel <a.s.hodel@eng.auburn.edu> |
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40 ## Adapted-By: jwe |
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41 |
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42 function retval = qmult (a, b) |
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43 |
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44 [a1, b1, c1, d1] = quaternion (a); |
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45 [a2, b2, c2, d2] = quaternion (b); |
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46 |
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47 ri = b1*c2 - c1*b2 + d1*a2 + a1*d2; |
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48 rj = c1*a2 - a1*c2 + d1*b2 + b1*d2; |
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49 rk = a1*b2 - b1*a2 + d1*c2 + c1*d2; |
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50 rr = -(a1*a2 + b1*b2 + c1*c2) + d1*d2; |
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51 |
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52 retval = quaternion (ri, rj, rk, rr); |
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53 |
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54 endfunction |
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55 |
