Hi all,

Attached is my params file. I have an "mkrule" node which has two children, the first of which is a "rule" node.

Some "rule" nodes take more "rule" nodes as children, or they can also take an "end" node instead of a "rule" node. The "end" node essentially ends the chain.

Thus, you can have something like this:

mkrule -> rule -> rule -> rule -> end

or this:

mkrule -> rule -> end

but not this:

mkrule -> end

So I defined a type set "rule-or-end" which contains the types rule and end. Now "mkrule" takes a rule as a parameter, and any rule takes a rule-or-end as a parameter.

The problem is that when I do this, I get this warning and exception:

In function set f0 for the GPTreeConstraints tc0, no terminals are given with the return type rule which is required by other functions in the function set or by the tree's return type.  Nearly all tree-builders in ECJ require the ability to add a terminal of any type for which there is a nonterminal, and at any time.  Without terminals, your code may not work.  One common indication that a tree-builder has failed due to this problem is if you get the MersenneTwister error 'n must be positive'.
PARAMETER: gp.tc.0
Initializing Generation 0
Exception in thread "main" java.lang.IllegalArgumentException: n must be positive
at ec.util.MersenneTwisterFast.nextInt(MersenneTwisterFast.java:1081)

The problem is that I can't make end return a rule (which would satisfy having a terminal of return type rule), because then mkrule -> end becomes a possibility.

Any idea how to solve this?