Mercurial > octave-nkf
annotate scripts/specfun/factorial.m @ 20354:227d582fa300 stable
build: Sort generated PKG_ADD contents consistently
* libinterp/mk-pkg-add: Set LC_COLLATE=C when sorting for consistent output.
| author | Mike Miller <mtmiller@octave.org> |
|---|---|
| date | Fri, 10 Jul 2015 01:10:30 -0400 |
| parents | 4197fc428c7d |
| children |
| rev | line source |
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maint: Update copyright notices for 2015.
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1 ## Copyright (C) 2000-2015 Paul Kienzle |
| 5820 | 2 ## |
| 3 ## This file is part of Octave. | |
| 4 ## | |
| 5 ## Octave is free software; you can redistribute it and/or modify it | |
| 6 ## under the terms of the GNU General Public License as published by | |
| 7016 | 7 ## the Free Software Foundation; either version 3 of the License, or (at |
| 8 ## your option) any later version. | |
| 5820 | 9 ## |
| 10 ## Octave is distributed in the hope that it will be useful, but | |
| 11 ## WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 13 ## General Public License for more details. | |
| 14 ## | |
| 15 ## You should have received a copy of the GNU General Public License | |
| 7016 | 16 ## along with Octave; see the file COPYING. If not, see |
| 17 ## <http://www.gnu.org/licenses/>. | |
| 5820 | 18 |
| 19 ## -*- texinfo -*- | |
| 20 ## @deftypefn {Function File} {} factorial (@var{n}) | |
| 19135 | 21 ## Return the factorial of @var{n} where @var{n} is a real non-negative integer. |
| 22 ## | |
| 23 ## If @var{n} is a scalar, this is equivalent to @code{prod (1:@var{n})}. For | |
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24 ## vector or matrix arguments, return the factorial of each element in the |
| 19135 | 25 ## array. |
| 26 ## | |
| 27 ## For non-integers see the generalized factorial function @code{gamma}. | |
| 28 ## Note that the factorial function grows large quite quickly, and even | |
| 29 ## with double precision values overflow will occur if @var{n} > 171. For | |
| 30 ## such cases consider @code{gammaln}. | |
| 31 ## @seealso{prod, gamma, gammaln} | |
| 5820 | 32 ## @end deftypefn |
| 33 | |
| 34 function x = factorial (n) | |
| 19135 | 35 |
| 6391 | 36 if (nargin != 1) |
| 37 print_usage (); | |
| 19135 | 38 elseif (! isreal (n) || any (n(:) < 0 | n(:) != fix (n(:)))) |
| 39 error ("factorial: all N must be real non-negative integers"); | |
| 5820 | 40 endif |
| 19135 | 41 |
| 6532 | 42 x = round (gamma (n+1)); |
| 19135 | 43 |
| 44 ## FIXME: Matlab returns an output of the same type as the input. | |
| 45 ## This doesn't seem particularly worth copying--for example uint8 would | |
| 46 ## saturate for n > 5. If desired, however, the following code could be | |
| 47 ## uncommented. | |
| 48 # if (! isfloat (x)) | |
| 49 # x = cast (x, class (n)); | |
| 50 # endif | |
| 51 | |
| 5820 | 52 endfunction |
| 6532 | 53 |
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54 |
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55 %!assert (factorial (5), prod (1:5)) |
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56 %!assert (factorial ([1,2;3,4]), [1,2;6,24]) |
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57 %!assert (factorial (70), exp (sum (log (1:70))), -128*eps) |
| 19135 | 58 %!assert (factorial (0), 1) |
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59 |
| 19135 | 60 %!error factorial () |
| 61 %!error factorial (1,2) | |
| 62 %!error <must be real non-negative integers> factorial (2i) | |
| 63 %!error <must be real non-negative integers> factorial (-3) | |
| 64 %!error <must be real non-negative integers> factorial (5.5) | |
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65 |