An open-source Mathematica. This repository contains the Python modules for WL Built-in functions, variables, core primitives, e.g. Symbol, a parser to create Expressions, and an evaluator to execute them.
And I will keep this branch open until everything is gone over. In particular, I see we don't describe the 3-argument ReplaceList form, but that will be coming up next.
Since you are okay, I will merge this now, but continue going over the changes.