On 10/21/2010 6:41 PM, Joel de Guzman wrote: > I like it when we are talking on a conceptual level :-). I think part > of the difficulty is in combining two domains: language/parsing and OOP.
<nod> > As much as I do not have any problems with "visitation", it's also > intersecting with the notion of "semantic actions". If we add yet one > more set of parlance: schemas and documents (which is not totally > unrelated -- schemas are basically just grammars), I'm afraid we'll > add more confusion. Thanks, Joel. Yes, let's not mix our metaphors. (But I do think that XML/Schema shares much with Language/Grammar. And a Proto expression is quite a lot like an XML DOM in that is has a tree structure, and the Schema describes the valid trees. But yes, we're talking about DSLs and compiler-construction toolkits, so I can keep the XML/Schema talk to myself. :-) > I'd say stick to only one domain's parlance. Since proto is closer to > the language/parsing domain, I think we should stick to (semantic)actions, > rules, grammars etc. This is my feeling as well. > If you want to go "meta" on parsing, then you might > get some inspiration on 2-level grammars (inspired by van Wijngaarden > grammars) with the notion of hyper-rules, etc. This document: > > http://www.cl.cam.ac.uk/~mgk25/iso-14977.pdf > > gives a better glimpse into 2-level grammars (see Annex A). > > "Although the notation (also known as a van Wijngaarden grammar, > or a W-grammar) is more powerful, it is more complicated and, > as the authors of Algol 68 recognized, “may be difficult > for the uninitiated reader”. > > I'm not really sure how this relates to the current design, but > I think we should be getting closer to this domain and it deserves > some notice. You're not the first to bring up vW-grammars in relation to Proto. Someone suggested them to implement EDSL type systems. I spent a good amount of time reading about them, and could get my head around it. My understanding is that they're powerfully descriptive, but that building compilers with vW-grammars is very expensive. I don't really know. I think I'd need to work with a domain expert to make that happen. Any volunteers? :-) -- Eric Niebler BoostPro Computing http://www.boostpro.com _______________________________________________ proto mailing list proto@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/proto
