MathJax tags for Octopress

math.rb

#--------------------------------------------------------------
#  MathJax tags for Octopress
#
#  Put this in the plugins folder.
#  Use a single "inlinemath" tag for inline math.
#  Use a pair of "math/endmath" tags for math as a standalone paragraph.
#  The "math" tag takes an optional size argument.
#  You also need to include MathJax in the page header, for example by adding
#      <script type="text/javascript" src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML"></script>
#  to source/_includes/custom/head.html
#
#  Examples:
#
#  ... our approximation takes the form {% inlinemath 1 - e^{-X} %}, because ...
# 
#  {% math %}
#  \frac{N-1}{N}\times\frac{N-2}{N}\times\dots\times\frac{N-(k-2)}{N}\times\frac{N-(k-1)}{N}
#  {% endmath %}
# 
#  {% math 170% %}
#  e^{\frac{-k(k-1)}{2N}}
#  {% endmath %}
#--------------------------------------------------------------

module Jekyll

  class MathBlock < Liquid::Block
    def initialize(tag_name, params, tokens)
      super
      @size = params.strip
    end

    def render(context)
      if @size == ''
        "$$ #{super} $$"
      else
        "<div style=\"font-size:#{@size};\">$$ #{super} $$</div>"
      end
    end
  end

  class InlineMathTag < Liquid::Tag
    def initialize(tag_name, params, tokens)
      super
      @text = params
    end

    def render(context)
      "\\\\(#{@text}\\\\)"
    end
  end

end

Liquid::Template.register_tag('math', Jekyll::MathBlock)
Liquid::Template.register_tag('inlinemath', Jekyll::InlineMathTag)