/usr/share/octave/packages/signal-1.3.0/bitrevorder.m is in octave-signal 1.3.0-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 | ## Copyright (C) 2007 Sylvain Pelissier <sylvain.pelissier@gmail.com>
## Copyright (C) 2013 Mike Miller
##
## This program 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.
##
## This program 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
## this program; if not, see <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn {Function File} {@var{y} =} bitrevorder (@var{x})
## @deftypefnx {Function File} {[@var{y} @var{i}] =} bitrevorder (@var{x})
## Reorder the elements of the vector @var{x} in bit-reversed order.
## Equivalent to calling @code{digitrevorder (@var{x}, 2)}.
## @seealso{digitrevorder, fft, ifft}
## @end deftypefn
function [y, i] = bitrevorder (x)
if (nargin != 1)
print_usage ();
elseif (! isvector (x))
error ("bitrevorder: X must be a vector");
elseif (fix (log2 (numel (x))) != log2 (numel (x)))
error ("bitrevorder: X must have length equal to an integer power of 2");
endif
[y, i] = digitrevorder (x, 2);
endfunction
%!assert (bitrevorder (0), 0);
%!assert (bitrevorder (0:1), 0:1);
%!assert (bitrevorder ([0:1]'), [0:1]');
%!assert (bitrevorder (0:7), [0 4 2 6 1 5 3 7]);
%!assert (bitrevorder (0:15), [0 8 4 12 2 10 6 14 1 9 5 13 3 11 7 15]);
%% Test input validation
%!error bitrevorder ();
%!error bitrevorder (1, 2);
%!error bitrevorder ([]);
%!error bitrevorder (0:2);
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