Futures Emacs should itself be written in emacs lisp For every part this seems pretty hard! But: This compiler can be used to bootstrap this process With type declarations and inferencing it can be as efficient as the C code Plenty of examples, e.g. provide or copy-alist It can also JIT compile parts as needed Type-generic operations like + would be better expressed using defgeneric and defmethod. then the compiler could more easily optimize? Not clear. Meanwhile there should be a rule about use of Fwhatever in Emacs Only “inlineable” uses should be permitted Things like Fload should indirect via Ffuncall This is very easy to do when translating from lisp It is bad that Emacs has 3 interpreters in it: Emacs Lisp Regexp CCL