# Pandoc Lua filter to convert math block type

I’ve been using Markdown for writing text, and converting it to different formats such as HTML and PDF. As a result, I am having to learn to live with differences between different converters such as Pandoc, which I use to render HTML and PDF, and Kramdown, which is used by Jekyll to render this page.

One particular difference is related to how you insert math using $$\LaTeX$$. Whereas Pandoc expects you to insert inline math between \$ signs, Kramdown expects you to use $$. Pandoc understands math between $$ as block math syntax and it will add a line break before and after the math. The math still gets rendered nicely but messes with the vertical flow of the text.

Since all the math I use is inline, I wrote a simple Pandoc filter in Lua to force any math block to be inline

function Math(meta)
--print(meta.mathtype.." "..meta.text)
-- force InlineMath
meta.mathtype = "InlineMath"
return meta
end


Assuming the code above is saved to a file called filter.lua, you can tell Pandoc to use the filter by adding --lua-filter filter.lua to its command line.

If you do want to display math in its own block, you can create a paragraph containing just the math

$\LaTeX$

Pandoc filters to the rescue!