# Copyright (C) 1996,1998 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 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 sys = fir2sys (num,tsam,inname,outname)
  #
  # outsys = fir2sys(num,{tsam,inname,outname})
  # construct a system data structure from FIR description
  # inputs:
  #   num: vector of coefficients [c0 c1 ... cn] of the SISO FIR transfer
  #        function C(z) = c0 + c1*z^{-1} + c2*z^{-2} + ... + znz^{-n}
  #   tsam: sampling time (default: 1)
  #   inname: name of input signal 
  #   outname: name of output signal
  # outputs:  sys (system data structure)
   
  #  Written by R. Bruce Tenison  July 29, 1994
  #  Name changed to TF2SYS July 1995
  #  updated for new system data structure format July 1996
  # adapted from tf2sys july 1996

  save_val = implicit_str_to_num_ok;
  implicit_str_to_num_ok = 1;

  #  Test for the correct number of input arguments
  if (nargin < 1 | nargin > 4)
    usage('sys=fir2sys(num[,tsam,inname,outname])');
  endif

  # let tf2sys do the argument checking
  den = [1,zeros(1,length(num)-1)];

  # check sampling interval (if any)
  if(nargin <= 1)               tsam = 1;		# default 
  elseif (isempty(tsam))        tsam = 1;		endif

  #  Set name of input
  if(nargin < 3)  inname = sysdefioname(1,"u");        endif

  #  Set name of output
  if(nargin < 4)  outname = sysdefioname(1,"y"); 	endif

  sys = tf2sys(num,den,tsam,inname,outname);
  
  implicit_str_to_num_ok = save_val;
endfunction