Indeed, I don't know about JRuby. I know about Scheme. There is no fast Scheme that JIT-compiles, that I know of. All the fast Lisp compilers that I know compil

Indeed, I don't know about JRuby. I know about Scheme. There is no fast Scheme that JIT-compiles, that I know of. All the fast Lisp compilers that I know compile ahead-of-time. If you know why they did this, pray tell :) As a language implementor yourself, you probably have a good feel for the cost accounting.