Thank you, Scott, for your help. That what I tried to understand. I'm going to use that with analytical integration/differentiation, but seems that I've got an idea. :) -- Peter.

Eh. I was not enough clear. The question is how do I define the following function: f(nu[1],nu[2])=nu[1]+nu[2];? You see, nu[1] and nu[2] are variables... I've told about array just because if I convert nu[1] into 1D math representation I got: nu[1] - array element. -- Peter. Maple v11.01