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1 ## Copyright (C) 2000, 2006, 2007 Paul Kienzle |
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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 3 of the License, or (at |
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8 ## your option) 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, see |
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17 ## <http://www.gnu.org/licenses/>. |
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18 |
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19 ## -*- texinfo -*- |
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20 ## @deftypefn {Function File} {} factorial (@var{n}) |
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21 ## Return the factorial of @var{n}. If @var{n} is scalar, this is |
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22 ## equivalent to @code{prod (1:@var{n})}. If @var{n} is an array, |
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23 ## the factorial of the elements of the array are returned. |
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24 ## @end deftypefn |
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25 |
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26 function x = factorial (n) |
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27 if (nargin != 1) |
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28 print_usage (); |
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29 elseif (any (n(:) < 0 | n(:) != round (n(:)))) |
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30 error ("factorial: n must all be nonnegative integers"); |
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31 endif |
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32 x = round (gamma (n+1)); |
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33 endfunction |
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34 |
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35 %!assert (factorial(5), prod(1:5)) |
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36 %!assert (factorial([1,2;3,4]), [1,2;6,24]) |
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37 %!assert (factorial(70), exp(sum(log(1:70))), -128*eps) |
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38 %!fail ('factorial(5.5)', "must all be nonnegative integers") |
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39 %!fail ('factorial(-3)', "must all be nonnegative integers") |
