Hello all. I want to be able to use Maple to do algebra with variables which do not commute with each other. Is there any way I can do this? Really, all I want to be able to do is specify that X*Y - Y*X != 0, and then have Maple recognise that for more complicated functions of X and Y. I have been looking through the documentation in the help system and have found no clues. Many thanks in advance for your help. Dave Abergel

Hi all I'm sorry for the immense stupidity of this question, but I've been reading Maple's help files for about an hour and I can't find the answer to this simple question. Maybe someone can enlighten me! What is the function that returns the length (by which I mean the number of elements) in a list? Thanks in advance Dave 8o)