# Copyright (C) 1993 John W. Eaton
# 
# 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 2, 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, write to the Free
# Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.

function retval = hadamard (k)

# usage: hadamard (k)
#
# Return the Hadamard matrix of order n = 2^k.
#
# See also: hankel, vander, hilb, invhilb, toeplitz

  if (nargin != 1)
    error ("usage: hadamard (n)");
  endif

  if (k < 1)
    retval = 1;
  else
    tmp = hadamard (k-1);
    retval = [tmp, tmp; tmp, -tmp];
  endif

endfunction