Hello Shamikan, A (array of) structures IS a mlist. The list of defined fields is returned by fieldnames(): --> s.b = %t; --> s.r = %pi; --> s.p = %z s = b: [1x1 boolean] r: [1x1 constant] p: [1x1 polynomial] --> fieldnames(s) ans = !b ! ! ! !r ! ! ! !p ! And the number of fields: --> size(fieldnames(s),1) ans = 3. Regards Samuel Gougeon