I'm designing a GP problem that has "ephemeral random constants" between its terminals. An ephemeral random constant gets a random value when created which is maintained constant during the rest of the evolution. Can I implement this with ECJ? How?. I'm not sure if each node in each GPTree is an instance in its own (which could then store values different to other instances) or pointers to a common class (in that case, how could I differentiate each node?). I have a similar problem also with the terminals, in the examples a different class is used for X and another for Y, in a two variable regression problem. I have vectors of data of size 64 (V), and I want to use a single class (namely, V[i]) and decide which value i has at creation time. Any help would be greatly appreciated, Alberto Cuesta