--- /dev/null
+## Copyright (C) 2009, 2010 Lukas F. Reichlin
+##
+## This file is part of LTI Syncope.
+##
+## LTI Syncope 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.
+##
+## LTI Syncope 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 LTI Syncope. If not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{bool} =} isstable (@var{sys})
+## @deftypefnx {Function File} {@var{bool} =} isstable (@var{sys}, @var{tol})
+## Determine whether LTI system is stable.
+##
+## @strong{Inputs}
+## @table @var
+## @item sys
+## LTI system.
+## @item tol
+## Optional tolerance for stability. Default value is 0.
+## @end table
+##
+## @strong{Outputs}
+## @table @var
+## @item bool = 0
+## System is not stable.
+## @item bool = 1
+## System is stable.
+## @end table
+##
+## @example
+## @group
+## real (p) < -tol*(1 + abs (p)) continuous-time
+## abs (p) < 1 - tol discrete-time
+## @end group
+## @end example
+## @end deftypefn
+
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: October 2009
+## Version: 0.2
+
+function bool = isstable (sys, tol = 0)
+
+ if (nargin > 2)
+ print_usage ();
+ endif
+
+ pol = pole (sys);
+ ct = isct (sys);
+
+ bool = __is_stable__ (pol, ct, tol);
+
+endfunction