On 18 Feb 2008, at 23:59, Andrea Censi wrote:
[...]
In a nutshell: given that Markdown.pl (and straight ports of it) do
processing using multiple passes of regex/replace, you cannot find a
syntax that captures Markdown.pl's behavior exactly.
I did a rule-based implementation which I have unfortunately since
lost¹.
A rule had 4 elements to it:
1. A regexp that makes the parser enter the context the rule
represents (e.g. block quote, list, raw, etc.).
2. A list of which rules are allowed in the context of this rule.
3. A regexp for leaving the context of this rule.
4. A regexp which is pushed onto a stack when entering the context of
this rule, and popped again when leaving this rule.
The fourth item here is really the interesting part, because it is
what made Markdown nesting work (99% of the time) despite this being
100% rule-driven.
The implementation of this did disagree with Markdown.pl on various
edge cases, but the spirit of Markdown was definitely there and it
felt way more predictable and flexible (e.g. you can have block quote
go directly after starting a list item, etc.)
It does however take a “no look-ahead”-approach, so e.g. `_` will
always enter emphasis, regardless of whether or not there is a closing
`_` later in the document.
¹ My main machine broke so I was working on a spare laptop while
waiting for a replacement, and it was on this machine I wrote the
Markdown parser, but I am afraid that the laptop saw a clean install
before I was able to copy the source to another machine :/
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