It depends on how you want to do loops.  What do you mean by
automatically-defined-loops exactly?  It seems to me that the
straightforward way is to just have a loop macro as one of your
nodes, whose eval() method looks something like this:

     result = empty
     n = eval first child
     loop n times or until MAX_ALLOWED_LOOPS:
         result = eval second child
     return result

Or you could have a while loop along these lines:

     count = 0;
     loop up to MAX_ALLOWED_LOOPS:
         n = eval first child
         if n == true then eval second child and return
     return empty


On Dec 7, 2005, at 7:55 PM, George Coles wrote:

> Hi,
>    Can anyone point me to an example of automatically defined loops
> that works with tree-based GP? Has anyone implemented loops in ECJ?
> I am
> contemplating beginning to add this feature to my copy of ECJ and it
> seems a bit daunting. Could the ADF stack be leveraged somehow to do
> this? As an aside, it seems odd that iteration and recursion are not
> more popular as a topic of discussion. I expect that I will really
> need
> iteration, at least, in my project, and I would think that many people
> would find it very valuable.
> Thanks
> George Coles