Request for comments on proposal for literate programming using markdown

Simon Hengel sol at
Mon Aug 13 11:23:20 CEST 2012

On Mon, Aug 13, 2012 at 08:45:51AM +0000, Philip Holzenspies wrote:
> >> However, it's a bit of an overspec'd package to link into the
> >> compiler, don't you think?
> > 
> > I did not mean to modify the Compiler.  Unliting is done by an
> > external program.  This already allows you to customize unliting
> > [2].
> Absolutely true, but I came across this in the GHC-source itself. I
> would like the GHC-source to be literateable (not a work, but you know
> what I mean) in markdown. Now, the GHC-source could be build with the
> same mechanism for having unlitting done by an external program, but
> that would make the build process depend on a very large library
> (through pandoc-unlit, depending on pandoc), which, by the way, has a
> GPL license.

I think it makes sense, that you do not want to depend on pandoc for
GHC's build process.  But would a more lightweight unlit for Markdown

Hmm, one issue could arise with a huge codebase (like GHC's) that uses
both traditional literate Haskell and Markdown.  You can't set the unlit
program globally then.  I think this could be solved by adding

    {-# OPTIONS_GHC -pgmL unlit-markdown #-}

to source files that use Markdown.  Sadly this is no valid Markdown, so
it is not really sane to add it to a Markdown file.

Would it work to adapt GHC's option sniffing, so that it recognizes
options in HTML comments (which are valid Markdown):

    <!-- OPTIONS_GHC -pgmL unlit-markdown -->

Possibly with the requirement that it has to be on the first line, and
maybe guarded by a flag (e.g. -ext-options-sniffing)?


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