## Copyright (C) 1996 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, 59 Temple Place, Suite 330, Boston, MA 02111 USA. 
 
## -*- texinfo -*-
## @deftypefn {Function File } { } sysout ( @var{sys}@{, @var{opt}@}) 
##  print out a system data structure in desired format
## @table @var
## @item  sys
##  system data structure
## @item  opt
## Display option
## @table @code
## @item []
##  primary system form (default); see @ref{sysgettype}.
## @item      "ss"
##  state space form
## @item      "tf"
##  transfer function form
## @item      "zp"
##  zero-pole form
## @item      "all"
##  all of the above
## @end table
## @end table
## @end deftypefn
 
function retsys = sysout(sys,opt)

  ## Written by A S Hodel: 1995-1996

  if( (nargin < 1) || (nargin > 2) )
    usage("sysout(sys[,opt])");
  endif

  if(isempty(sys))
    retsys = sys;
    warning("sysout: empty system")
    return;
  endif

  if(! is_struct(sys))
    disp("sysout: input must be a system structure")
  endif

  ## set up output type array
  if( nargin == 1 )
    opt = sysgettype(sys);
  else
    if( ! (strcmp(opt,"ss") + strcmp(opt,"tf") + ...
      strcmp(opt,"zp") + strcmp(opt,"all") ) )
      error("opt must be one of [], \"ss\", \"tf\", \"zp\", or \"all\"");
    endif
  endif

  ## now check output for each form:
  [nn,nz,mm,pp] = sysdimensions(sys);
  if( mm > 0)
    disp("Input(s)")
    disp(outlist(sysgetsignals(sys,"in"),"	"));
  else
    disp("Input(s): none");
  endif
  if (pp > 0)
    disp("Output(s):")
    disp(outlist(sysgetsignals(sys,"out"), ...
	  "	",sysgetsignals(sys,"yd")) );
  else
    disp("Output(s): none");
  endif
  if(sysgettsam(sys) > 0)
    disp(["Sampling interval: ",num2str(sysgettsam(sys))]);
    str = "z";
  else
    str = "s";
  endif

  ## transfer function form
  if( strcmp(opt,"tf") + strcmp(opt,"all") )
    sys = sysupdate(sys,"tf");		#make sure tf is up to date
    disp("transfer function form:")
    [num,den] = sys2tf(sys);
    tfout(num,den,str);
  endif

  if( strcmp(opt,"zp") + strcmp(opt,"all") )
    sys = sysupdate(sys,"zp");		#make sure zp is up to date
    disp("zero-pole form:")
    [zer,pol,kk] = sys2zp(sys);
    zpout(zer, pol, kk,str)
  endif

  if( strcmp(opt,"ss") + strcmp(opt,"all") )
    sys = sysupdate(sys,"ss");
    disp("state-space form:");
    disp([num2str(nn)," continuous states, ", num2str(nz)," discrete states"]);
    if( nn+nz > 0)
      disp("State(s):")
      xi = (nn+1):(nn+nz);
      xd = zeros(1,nn+nz);
      if(!isempty(xi))
	xd(xi) = 1;
      endif
      disp(outlist(sysgetsignals(sys,"st"),"	",xd));
    else
      disp("State(s): none");
    endif

    ## display matrix values?
    dmat = (max( [ (nn+nz), mm, pp ] ) <= 32);

    printf("A matrix: %d x %d\n",sysdimensions(sys,"st"),
	   sysdimensions(sys,"st"));
    [aa,bb,cc,dd] = sys2ss(sys);
    if(dmat) 	disp(aa); 	endif

    printf("B matrix: %d x %d\n",sysdimensions(sys,"st"),
	   sysdimensions(sys,"in"));
    if(dmat)     disp(bb);              endif

    printf("C matrix: %d x %d\n",sysdimensions(sys,"out"),
	   sysdimensions(sys,"st"));
    if(dmat) disp(cc);		endif

    printf("D matrix: %d x %d\n",sysdimensions(sys,"out"),
	   sysdimensions(sys,"in"));
    if(dmat)       disp(dd);         endif
  endif

  if(nargout >= 1)
    retsys = sys;
  endif 

  ## restore global variable

endfunction