Array function & atvalue()



Hello,
	I am trying to define a generic equation for position vectors, and to 
establish initial conditions in the following way:
START****************************************************************
Maxima 5.24.0 http://maxima.sourceforge.net
using Lisp SBCL 1.0.40.0.debian
Distributed under the GNU Public License. See the file COPYING.
Dedicated to the memory of William Schelter.
The function bug_report() provides bug reporting information.
(%i1) r[n](t):=%e^(%i*%theta[n](t));
                                       %i %theta (t)
                                                n
(%o1)                      r (t) := %e
                             n
(%i2) atvalue(theta[4](t),[t=0],%pi);

atvalue: improper argument: theta (t)
                                  4
  -- an error. To debug this try: debugmode(true);
END*******************************************************************


The reason for which I want to do this, is because, I want to define a 
kinematic chain like this:
START****************************************************************
(%i3) r[3](t)=r[1](t)+r[2](t);
                 %i %theta (t)     %i %theta (t)     %i %theta (t)
                          3                 2                 1
(%o3)         %e              = %e              + %e
END*******************************************************************


Based on experience, I know that atvalue() can only receive either a 
function like:
START****************************************************************
(%i4) atvalue(theta[t],[t=0],%pi);
(%o4)                                 %pi
(%i5) atvalue(theta(t),[t=0],%pi);
(%o5)                                 %pi
END*******************************************************************


Basically, I want to be able to define a function with the subscripted 
notation, and establish boundary conditions as well. Is that possible? 
Should I be trying to modify the atvalue() function by myself? I don't 
want to go through that trouble (I want to know if there is another 
option first). Can you help me? Thanks.


Edgar
-- 
--
TU Delft
Faculty of industrial design engineering
Product engineering section
Landbergstraat 15, Delft, 2628CE, Nederland
Office number: 32 B-0-320
Phone number +31 015 27 86367