I'm converting Markdown to PDF via LaTeX, with indent:true, and I'm using horizontal rules as scene or section breaks. I found the indent on the first paragraph after such a break ugly and wanted to do an automatic \noindent after every horizontal rule. This turned out to be pretty easy with a Haskell filter.

As it's the first time I've written anything in Haskell, I thought I'd post it here for feedback. Seems to me like maybe there's a more concise way to do the same thing.

Also this could obviously be adapted to actually remove the horizontal rules and replace them with the Pandoc internal representation of a vertical skip or blank line (whatever that is).

import Text.Pandoc.JSON

main :: IO ()

main = toJSONFilter noIndentAfterHorizontalRule

noIndentAfterHorizontalRule :: Pandoc -> Pandoc

noIndentAfterHorizontalRule doc =

let Pandoc meta blocks = doc

in Pandoc meta (mapAfterHorizontalRule noIndentifyPara blocks)

mapAfterHorizontalRule :: (Block -> Block) -> [Block] -> [Block]

mapAfterHorizontalRule f (HorizontalRule : block : blocks) =

HorizontalRule : f block : mapAfterHorizontalRule f blocks

mapAfterHorizontalRule f (block : blocks) = block : mapAfterHorizontalRule f blocks

mapAfterHorizontalRule f [] = []

noIndentifyPara :: Block -> Block

noIndentifyPara (Para xs) =

Para (RawInline (Format (Data.Text.pack "tex")) (Data.Text.pack "\\noindent ") : xs)

noIndentifyPara x = x