In gp:  I have a boolean function GreaterThan that I use to compare two
variables, but I want to make sure that I am not comparing the same two
variables.  In other words,

> var1  var2  is ok, and
> var1  var2  is ok, but
> var1 var1 is not ok, and
> var2 var2 is not ok either.

Here is the node constraint for the boolean function (from params file): = = ncBool-Child1Nil-Child2Nil = bool = 2 = nil = nil

Is there a way to restrict this behavior in the params file?  The children
will be of the same type, but can't be the same variable.  Or do I have to
do something in the checkConstraints method of the GPNode?