## Copyright (C) 1998 Auburn University.  All rights reserved.
##
## 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} {} sysgettype (@var{sys})
## return the initial system type of the system
##
## @strong{Input}
## @table @var
## @item sys
## System data structure.
## @end table
##
## @strong{Output}
## @table @var
## @item systype
## String indicating how the structure was initially
## constructed. Values: @code{"ss"}, @code{"zp"}, or @code{"tf"}.
## @end table
##
## @acronym{FIR} initialized systems return @code{systype="tf"}.
## @end deftypefn

function systype = sysgettype (sys)

  if (! isstruct (sys))
    error ("sysgettype: input sys is not a structure");
  endif

  typestr = {"tf", "zp", "ss"};
  systype = typestr{ sys.sys(1) + 1};

endfunction