Markdown Extra Spec: Parsing Section

[Michel Fortin]

Le 2008-05-13 à 2:20, John MacFarlane a écrit :


> PS. Here's all you have to learn in order to write or read a PEG  

> grammar.

>

> A B C                 A followed by B followed by C

> A | B                 A or B (ordered choice)

> A+                    one or more As

> A*                    zero or more As

> A?                    optional A

> !A                    not followed by A

> &A                    followed by A (but does not consume A)

> (A B)                 grouping

> .                     matches any character

> 'x'                   matches the character 'x'

> "string"              matches the string "string"

> [a-z]                 matches a character from 'a' to 'z'


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 
 >


Michel Fortin
michel.fortin at michelf.com
http://michelf.com/