I still am not sure exactly how to define it, but it's a ruby library, that is mix of a rules engine+spreadsheet feelings+array language+static validation+compiled/codegen... that last part is mostly not merged yet but yeah, ruby DSL codegenerating ruby, it's ruby all the way.

https://github.com/amuta/kumi/tree/codegen-v5 (see ./golden for more context on the compilation/codegen. I barely knew what a compiler was before doing this so I might have just created some nonsense )