> So it has to count from cc down to 0. Since cc is not an integer, there
> is a problem.
I see, thank you.
> Now how to fix this? What would you like to see? perhaps
>
> aa
> <cc>
> bb
>
> or an error message?
> or ??
I'm not sure. This is what a competitor does:
In[1]:= OutputForm @ Derivative[n,0,m][f][x,y,z]
Out[1]//OutputForm=
(n,0,m)
f [x, y, z]
Martin