CodeDown = Markdown as the universal language for program documentation

bucephalus org at
Mon Apr 11 12:17:55 EDT 2011

Dear Markdown enthusiasts out there!

Sure, I don't need to tell you how great an versatile Markdown is for
writing standard documents.
I think, that it would make a really great universal standard as a
programming documentation language, too, and maybe "CodeDown" would be a
good title for this approach.

The idea started when I was trying to document some PHP scripts. I need to
use different programming languages for different purposes, but I am not a
full time programmer. The problem is, that for most of these languages, the
standard documentation tools are yet another language on their own, and I
already have difficulties remembering the idioms of the programming
languages. When I was working on the PHP scripts, I was looking for a
standard tool to write some docs, but I was overwhelmed by phpDocumentor.

In the past, I often used Perl's POD to write tutorials for some of my
programs, and that always did a good job. But a while ago I discovered
Markdown, and I found that even more convenient and intuitive. I thought, it
would be very easy to use that as the format for literal programming in PHP:
by a simple modification of the usual comment delimiters /* ... */ and // in
PHP, these comments would become designated blocks for Markdown comments or
delimiters for source code parts, that would appear in the documentation.
The possibility these literal code blocks is an essential part of Donald
Knuth's literal programming concept, and most standard documentation tools
are not even capable of realizing that.

In a first conversion step, these blocks would turn into Markdown, and in a
second conversion step, the Markdown is converted to HTML.

PHP source code ------------------------------> Markdown
--------------------------> HTML

For the markdownToHtml function, I used Michel Fortin's PHP Markdown, so my
actual converter is a pretty small script. I called it ElephantMark (see and the
according script is its own documentation.

This approach can be used for any mainstream programming language. My
current favorite is Haskell, and I wrote a HaskellDown module, that does
similar things for Haskell. The main converter is just a composition of two

Haskell source code ---------------------------------> Markdown
------------------------> HTML

For the markdownToHtml part I used the very powerful Pandoc module, written
by John MacFarlane.
This week, I'll give a talk about it on a meeting of the Dutch Haskell User
Group, and I intend to publish it, as soon as possible.

During the preparations for the talk, I thought I should call the whole idea
"CodeDown", including "Php(Code)Down" as the CodeDown for PHP,
"PythonCodeDown" as the CodeDown for Python, etc. There could even be a
general CodeDown tool, that does the conversion for all these particular
languages alltogether.

But before I put any more work into this project, I would like to find out,
if there is really a general interest or support for this idea. Please,
don't spare on your comments, answers or questions.

Greetings, Thomas
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