## 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, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
## 02110-1301 USA.

## -*- texinfo -*-
## @deftypefn {Function File} {} gram (@var{a}, @var{b})
## Return controllability gramian @var{m} of the continuous time system
## @math{dx/dt = a x + b u}.
##
## @var{m} satisfies @math{a m + m a' + b b' = 0}.
## @end deftypefn

## Author: A. S. Hodel <a.s.hodel@eng.auburn.edu>

function m = gram (a, b)

  ## Let lyap do the error checking...

  m = lyap (a, b*b');

endfunction