testing python-markdown

[John Gruber]

Yuri T. <qaramazov at gmail.com> wrote on 08/13/05 at 7:42 pm:


> 1. Lack of support for nested braces ([[braces]](url)) - I can't think

> of an easy way of adding this for the lack of python equivalent of

> perl's recursive regexps.  I am not sure it's worth it.


That's a shame. Does it help if you look at Michel's PHP
implementation? PHP doesn't have recursive patterns the same way
Perl does, but Michel has worked around it. I just glanced at the
source for an older version of PHP Markdown, and it looks like he's
just doing it by looking for nested `[]` pairs up to 6 levels deep
-- which for all practical purposes is deep enough.



> 2. <p> tags in "loose" lists - I missed this rule earlier and now

> figured out that I my current design makes it hard to implement it. 

> (When I am processing a list item I don't know what kind of a list

> it's a part of.)  This does seem like an important feature, so I will

> think about it more when I am in a procrastination mode.


So your lists never add <p> tags?



> 3. Markdown.pl converts "+\tText" to "+   Text", i.e. it uses THREE

> tabs.   What is the actual rule there?  I can see that Markdown.pl

> handles tabs via $text =~ s{(.*?)\t}{$1.(' ' x ($g_tab_width -

> length($1) % $g_tab_width))}ge; but this looks like line noise to

> me...  Can someone provide pseudo-code for this?


Tab stops aren't "four spaces", they're "move to the next column
that's a multiple of 4". Although instead of hard-coding 4,
Markdown.pl uses a global, $g_tab_width.

So what we have is the regex:

    (.*?)\t

which says to lazily capture everything up to the first tab
character, saving it in group $1.

Then we have the substitution:

    {$1.(' ' x ($g_tab_width - length($1) % $g_tab_width))}ge;

which, because of the /e option, isn't just a pattern, but is Perl code.

$1 is the text before the tab, and we put it back in the replacement.

Then we replace the tab with the right number of spaces. The right
number of spaces is

    4 - length($1) % 4

In Perl, the x operator is like a multiplicative concatenator for
strings.

    'j' x 4

returns

    jjjj

Hope this helps,

-J.G.