update packages

[CreaPhase.git] / octave_packages / m / specfun / perms.m

diff --git a/octave_packages/m/specfun/perms.m b/octave_packages/m/specfun/perms.m
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+## Copyright (C) 2001-2012 Paul Kienzle
+## Copyright (C) 2009 VZLU Prague
+##
+## This file is part of Octave.
+##
+## Octave is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 3 of the License, or (at
+## your option) any later version.
+##
+## Octave is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+## General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING.  If not, see
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} perms (@var{v})
+##
+## Generate all permutations of @var{v}, one row per permutation.  The
+## result has size @code{factorial (@var{n}) * @var{n}}, where @var{n}
+## is the length of @var{v}.
+##
+## As an example, @code{perms([1, 2, 3])} returns the matrix
+##
+## @example
+## @group
+##   1   2   3
+##   2   1   3
+##   1   3   2
+##   2   3   1
+##   3   1   2
+##   3   2   1
+## @end group
+## @end example
+## @end deftypefn
+
+function A = perms (v)
+  if (nargin != 1)
+    print_usage ();
+  endif
+  v = v(:);
+  n = length (v);
+
+  if (n == 0)
+    A = [];
+  else
+    A = v(1);
+    for j = 2:n
+      B = A;
+      A = zeros (prod (2:j), n, class (v));
+      k = size (B, 1);
+      idx = 1:k;
+      for i = j:-1:1
+        A(idx,1:i-1) = B(:,1:i-1);
+        A(idx,i) = v(j);
+        A(idx,i+1:j) = B(:,i:j-1);
+        idx += k;
+      endfor
+    endfor
+  endif
+endfunction
+
+%!error perms ();
+%!error perms (1, 2);
+
+%!assert (perms ([1,2,3]), [1,2,3;2,1,3;1,3,2;2,3,1;3,1,2;3,2,1]);
+%!assert (perms (1:3), perms ([1,2,3]));
+
+%!assert (perms (int8([1,2,3])), int8([1,2,3;2,1,3;1,3,2;2,3,1;3,1,2;3,2,1]));