Sorry for troubling you with a newbie question on ECJ.
My problem is similar to common GP problems. Say, finding a
solution like 'A+B*C/D'. One thing special is that valid individuals need
to satisfy two constraints:
1) Certain variables can only appear in the individual if certain other
variables appear. For example, X can appear in the individual if only Y
appears. Then 'X+A/Y' and "C-Y" are valid individuals, while 'B+X' is not.