I will add another example sometime. In the meantime, why not try writing your own. Some kind of diagnostic system is best, that starts off with symbols denoting ``symptoms'' (in the broadest sense, e.g. they could be the names of geological features, or of pop groups, from which you infer the type of rocks present underground, or the type of rock music someone likes). If you imitate the example above you should have no problem. The handout on Editing your own programs gives, at its end, some info on program structure.