[ragel-users] Ragel pointers

[Adrian Thurston]

I've never made a wikitext parser using ragel but it looks reasonable to 
me. First you organize by lines, then by what can appear on them. There 
are probably a number of ways to parse wikitext. You should go with the 
one that's most natural for you.

-Adrian

Matt Reynolds wrote:
> So, I've been struggling on and off for some time with creating a
> lightweight "humane text" parser with Ragel.  Here's what I've got.
> 
> %%{
> machine simtex;
> 
> 	newline = "\n" @ { curline++; newline(); };
> 
> 	text = (print -- newline)* >{ markTextStart(fpc);} %
> { captureText(fpc);};
> 
>     comment_to_eol = "#!" %{ fire(Token.Type.COMMENT);} ;
> 
>     heading = "%" {1,5} % { fire(Token.Type.HEADING); };
>     separator = "-" {5,} % { fire(Token.Type.SEPARATOR); };
> 
>     set = "*" {1,5} @ { fire(Token.Type.SET); };
>     list = ([0-9]+ . ".") {1} @ { fire(Token.Type.LIST); };
> 
>     uninterpolated_command_start = "$<{";
>     uninterpolated_command_end = "}>$";
> 
>     stanzas = (comment_to_eol | heading | separator | set | list);
> 
> 	main := (stanzas? . text . newline+ )*;
> }%%
> 
> I've tried various permutations, with some success, but this is the
> configuration that has yielded the most results.  I'm attempting to
> parse text in two passes, with the first pass catching all line-based
> formatting and the second catching any inter-line formatting.
> 
> At this point, I'm just looking for some more general explanation of
> best practices for how to write parsers like this in Ragel.  I've
> followed the examples, and each time I come back to this hobby project
> I understand a little more, but I figured I'd ask if people have
> general tips (or more full fledged examples) of how to write these
> sorts of parsers in Ragel.
> 
> I've looked around for other examples of wiki-text parsers and what
> not, but they're generally very complicated and very lengthy, which
> seem to go against the elegance that Ragel embodies.
> 
> Anyway, thanks for any help you might be able to give,
> Matt
>