ULMUL
ULMUL is an original Ultra Lightweight MarkUp Language.
You can write TeX-style equations in ULMUL texts.
The ULMUL texts can be converted
into HTML5+MathML with ulmul2html5 command,
into HTML5+MathJax with ulmul2mathjax and
into LaTeX with ulmul2latex.
You can also generate
Slidy presentations.
Its library ulmul.rb is written in Ruby.
Repository of ULMUL: https://github.com/t-nissie/ULMUL
Documents of ULMUL, index.ja.html and index.en.html, will be installed ...SOMEWHERE.../lib/ruby/gems/4.0.0/gems/ulmul-0.8.1/.
ulmul is under continuous integration (CI) at GitHub Actions: