--- /dev/null
+## Copyright (C) 2011 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 -*-
+## check alpha for model reduction commands
+
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: November 2011
+## Version: 0.1
+
+function alpha = __modred_check_alpha__ (alpha, dt)
+
+ if (! is_real_scalar (alpha))
+ error ("modred: argument alpha must be a real scalar");
+ endif
+ if (dt) # discrete-time
+ if (alpha < 0 || alpha > 1)
+ error ("modred: require 0 <= ALPHA <= 1");
+ endif
+ else # continuous-time
+ if (alpha > 0)
+ error ("modred: require ALPHA <= 0");
+ endif
+ endif
+
+endfunction