The Guile 2.0 branch. I don&#x27;t know what magic optimisation dust they sprinkled over the upcoming 2.2, but it sure is fast.<p>We thought about using chicken, but it depends quite a lot on using  syntax-case to deconstruct everything, and I didn&#x27;t want to learn their implicit renaming stuff.<p>Apparently the 2.2 branch has full elisp support. Can&#x27;t wait for Emacs to run on it.