> While we are on this subject... How do you troubleshoot camlp4 rules?

Not sure what you mean :(

> With a stream parser you can invoke individual functions since each is a 
> full-blown parser. Can the same be done with camlp4, e.g. individual rules 
> invoked?

Well when you invoke the parser with Gram.parse, you give it the entry point. So you may parse only a subset of your language if the grammar allows it.

> Can rules be traced to see which ones are being taken?

Erm, I don't really know... You can always printf when a rule is taken, but I'm not aware of a built-in construct that allows you to monitor the rules that are taken.

Cheers,
Matthieu