Let me do the math

As this is my site and a big part of my life is math, I’d obviously like to have the possibility to use mathematical formulae here.

So after looking around for a while I found out, that Maruku the standard Markdown engine of Jekyll is able to use e.g. ritex, or blahtex to convert Latex formulae into MathML or png images. A little investigation into Jekyll later I knew that it only uses blahtex for conversion of formulae into png images (if that’s wrong drop me a line in the comments please). Since I really like modern web standards this was unacceptable for me and I took a stab into writing my first Jekyll plugin.

As most of the formulae I use will be rather short, at least at first. I thought I’d start with something that can do short formulae easy and find a solution for the inevitable giant formula later. I still liked to keep my blog compiling automatically after I push it to my git repository and Latex is not installed on my hosting provider uberspace. I could do that, but just for having some formulae on my blog seemed a bit excessive. So I started out going for a pure ruby setup with ritex, just to find out that it can’t even parse a simple array environment. This was equally unacceptable.

Next iteration: itex2mml which is a standalone program in a single binary and has ruby bindings. After downloading and copying into my path, the next challenge arose. How the hack is the ruby binding package called? Actually searching for it was no fun at all and didn’t find me a solution either, so I went back and fumbled around in the Maruku source code since it is one of the supported options for a rendering engine. With the pleasant surprise that I could keep the code almost unchanged. And a little furious with the naming convention of this package. itex2mml, Itex2MML and itextomml come on! Who the heck does something like that.

require 'itextomml'

module Jekyll
  class TexTag < Liquid::Tag
  
    def initialize (tag_name, text, tokens)
      super
      @text = text
    end 

    def render(context) 
      p = Itex2MML::Parser.new

      '<div class="mathLatexToMML">' << p.block_filter("#{@text}") << '</div>'
    end
  end
  class TexBlock < Liquid::Block
  
    def initialize (tag_name, text, tokens)
      super
    end 

    def render(context) 
      p = Itex2MML::Parser.new

      '<div class="mathLatexToMML">' << p.block_filter(super) << '</div>'
    end
  end
end 

Liquid::Template.register_tag('latex', Jekyll::TexTag)
Liquid::Template.register_tag('latexblock', Jekyll::TexBlock)

<script type="text/javascript" src="https://c328740.ssl.cf1.rackcdn.com/mathjax/latest/MathJax.js?config=MML_HTMLorMML.js"></script>

{%latex e^{\pi\cdot i}+1=0 %}

{%latexblock%}
fib(n)=\pi_2 \left(\left(\begin{array}{cc}1 & 1 \\ 1 & 0\end{array}\right)^{n-1}\cdot\left(\begin{array}{c}1\\1\end{array}\right)\right)
{%endlatexblock%}