On 10/22/2010 10:01 AM, Eric Niebler wrote:
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? :-)
Heh, people make it look needlessly complicated than it really is :-)
Check out the doc I sent (Annex A). It's really, to my mind,
generic languages -- abstraction of rules and templated grammars
through metanotions and hyper-rules. I have this strong feeling that
that's the intent of Thomas and your recent designs. Essentially,
making the phoenix language a metanotion in itself that can be
extended post-hoc through generic means.
Regards,
--
Joel de Guzman
http://www.boostpro.com
http://spirit.sf.net
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