## Copyright (C) 2007 Sylvain Pelissier <sylvain.pelissier@gmail.com>
##
## 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; see the file COPYING. If not, see
## <https://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn {Function File} {} bohmanwin (@var{m})
## Return the filter coefficients of a Bohman window of length @var{m}.
## @seealso{rectwin, bartlett}
## @end deftypefn

function w = bohmanwin (m)

  if (nargin != 1)
    print_usage ();
  elseif (! (isscalar (m) && (m == fix (m)) && (m > 0)))
    error ("bohmanwin: M must be a positive integer");
  endif

  if (m == 1)
    w = 1;
  else
    N = m - 1;
    n = -N/2:N/2;

    w = (1-2.*abs(n)./N).*cos(2.*pi.*abs(n)./N) + (1./pi).*sin(2.*pi.*abs(n)./N);
    w(1) = 0;
    w(length(w))=0;
    w = w';
  endif

endfunction

%!assert (bohmanwin (1), 1)
%!assert (bohmanwin (2), zeros (2, 1))

%% Test input validation
%!error bohmanwin ()
%!error bohmanwin (0.5)
%!error bohmanwin (-1)
%!error bohmanwin (ones (1, 4))
%!error bohmanwin (1, 2)
