I am new to ECJ and can I start by saying that it looks a great package and thanks for making it available.
My question is probably very basic as I am just getting to grips with the system (and learning Java as I go). I am trying to build a strongly typed GP system where the terminals are of type String, some functions take string arguments and return Booleans and others take Boolean arguments and return Booleans. Each GP returns a Boolean. When I try to implement this I get an error from GPTreeConstraints saying that: "no terminals are given with the return type Boolean which is required by other functions in the function set. PARAMETER: gp.tc.0 "
But in my case I don't want to have any Boolean terminals. Any help appreciated,