Eric Niebler wrote: > On 12/10/2010 3:23 AM, Thomas Heller wrote: <snip> >> However, the solution I am looking for is different. >> The sub-domain i tried to define should also extend its super domain, BUT >> expressions valid in this sub-domain should not be valid in the super >> domain, only in the sub-domain itself. > > Because you don't want phoenix::_a to be a valid Phoenix expression > outside of a phoenix::let, right?
Correct. >> I think proto should support both forms of operation. The first one can >> be easily (more or less) achieved by simply changing proto::matches in >> the way you demonstrated earlier, I think. I am not sure, how to do the >> other stuff properly though. > > OK, let's back up. Let's assume for the moment that I don't have time to > do intensive surgery on Proto sub-domains for Phoenix (true). How can we > get you what you need? Good question :) I can maybe help here once the port is finished once and for all. Let's prioritize. Too bad your day job does not involve proto :( > My understanding of your needs: you want a way to define the Phoenix > grammar such that (a) it's extensible, and (b) it guarantees that local > variables are properly scoped. You have been using proto::switch_ for > (a) and sub-domains for (b), but sub-domains don't get you all the way > there. Have I summarized correctly? Absolutely! > My recommendation at this point is to give up on (b). Don't enforce > scoping in the grammar at this point. You can do the scope checking > later, in the evaluator of local variables. If a local is not in scope > by then, you'll get a horrific error. You can improve the error later > once we decide what the proper solution looks like. I tried that and failed miserably ... There might have another workaround, I already have something i mind i missed earlier. > If I have mischaracterized what you are trying to do, please clarify. Nope, I guess this is the way it should be. Please disregard my other mail in this thread ;) _______________________________________________ proto mailing list proto@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/proto
