Hi all, New to GP and ECJ so please bear with me, Two questions, 1 Has anyone found a solution which avoids building a unique class for every variable in a problem. Say you have over a thousand variables, is there a way to define a single class which returns different variables ??? (I believe this is partly due to how java works) 2 Is there a way to define a function, say summation or the like, that accepts various number of children ??? Is there a way to define a class that takes from zero to x number of children and is not hard coded in params files but is program created ??? Thanks for all you help, Vlad