## 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} {@var{retsys} =} syschtsam (@var{sys}, @var{tsam})
## This function changes the sampling time (tsam) of the system.  Exits with
## an error if sys is purely continuous time.
## @end deftypefn

## Author: John Ingram <ingraje@eng.auburn.edu>
## Created: August 1996

function retsys = syschtsam (sys, tsam)

  if (nargin != 2)
    usage("retsys = syschtsam(sys,tsam)");
  elseif (!is_struct(sys))
    error("sys must be in system data structure form");
  elseif(!is_scalar(tsam))
    disp("syschtsam:")
    tsam
    error("tsam must be a scalar")
  elseif ( ! (is_sample(tsam) | (tsam == 0) ) )
    error("tsam must be real, scalar, and greater than zero");
  elseif (sysgettsam(sys) == 0)
    [nc,nz,mm,pp] = sysdimensions(sys);
    warning("syschtsam: continuous system (nc=%d, nz=%d, mm=%d, pp=%d)", ...
      nc,nz,mm,pp);
    warning("syschtsam: The system is continuous, use c2d to make the system discrete");
  endif

  retsys = sys;
  retsys.tsam = tsam;

endfunction