Markdown Extra Spec: Parsing Section

[John MacFarlane]

> It certainly true that many parts could be converted to this and be less 

> verbose, and I find this idea appealing. I doubt the whole Markdown Extra 

> ruleset can be expressed in this format though. Can a PEG grammar have 

> parametrized rules?

>

> I've just added nested block element support in the spec. This is done  

> by having the block element generator (formerly the block element pass) 

> have a stack of rules to match when starting each line. This idea coming 

> straight from Allan Odgaard's explanation of his lost Markdown parser.

> <http://six.pairlist.net/pipermail/markdown-discuss/2008-March/001107.html 


No, PEG can't do this. But there is a different approach that works
(described in my earlier email).

By the way: if I understand it correctly, your description of "Code
block" would parse the following as two code blocks, not one code block
containing a blank line:

    some code

    more code

(Note: there is no tab on the middle line.)  I don't think that's the
desired behavior.

Here's the markdown-peg version (and remember, this is "runnable"):

verbatim <- newRule $ 
   many1 (doesNotMatch blankline ->> indentedLine) <++> 
   (many (many1 (optional indent ->> blankline) <++> 
          many1 (doesNotMatch blankline ->> indentedLine)) ## concat) <<- 
   many blankline ## Verbatim . concat

John