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annotate scripts/specfun/factorial.m @ 9141:c1fff751b5a8

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Update section 17.1 (Utility Functions) of arith.txi Split section into "Exponents and Logarithms" and "Utility Functions" Use Tex in many more of the doc strings for pretty printing in pdf format.
author Rik <rdrider0-list@yahoo.com>
date Mon, 20 Apr 2009 17:16:09 -0700
parents 1bf0ce0930be
children 8c71a86c4bf4
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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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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 a scalar, this is
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22 ## equivalent to @code{prod (1:@var{n})}. For vector or matrix arguments,
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23 ## return the factorial of each element in the array.
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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")