Look at all of them, then throw them away. Start with a lexer, a parser (pretty easy), the AST is already done, then it's all about the eval loop. All you need

Look at all of them, then throw them away. Start with a lexer, a parser (pretty easy), the AST is already done, then it's all about the eval loop. All you need is sit down until you understand Lisp's metacircular evaluator (less than 50 lines or code), which is all you need to implement eval. (I found this while writing this comment: https://bernsteinbear.com/blog/lisp/12_metacircular/ https://bernsteinbear.com/blog/lisp/12_metacircular/)