Re: Formal description of Org files

[Rustom Mody <rustompmody@gmail.com>]

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>
> Hi,
>
> I have a question.
>
> At FOSDEM, someone asked me if there was a formal description of the
> structure of Org files, in some language
> that would be the input for a parser (or parser generator?) so that Org
> file could be easily parsed.
>
> Unfortunately I did not catch the name of the format description language
> that could be
> used for something, not did I catch the name of the person who talked to
> me.
>
> Can anyone help out here?  Let me know what language to use, and maybe help
> work on such a formal description?  I
> think it would be useful to have....
>

Something like yacc (bison, antlr etc) are all 'executable BNF' languages.
 When they work they can make the code an order of magnitude smaller and
development/programming correspondingly easier.

That said I see a couple of hitches.

1. Grammatical handling of languages is based on the assumption of a clear
and well defined set of tokens/lexemes.  I expect this would be harder in
org than the typical programming languages for which yacc etc are used.  For
example in most 'normal' languages there are comments and strings.  These
involve some non trivial handling which is entirely hidden from the grammar
by being pushed into the lexer.

2. Parsing a program is done for the full program as a rule (IDEs are the
exception to the rule). Sensible parsing of program fragments, where the
fragmenting could be quite arbitrary, is a bit of a research problem

3. As I see it, the main declarative tool (somewhat akin to grammars) that
org uses is regular expressions.  IOW org is written with re-s strung
together with programming logic ie vanilla elisp.  An alternative that stays
within the regular framework (not using the heavy guns of context free
parsing) may be ragel: http://www.complang.org/ragel/

Rusi

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