It helps. Chicken seems to support exactly that: https://wiki.call-cc.org/man/5/Types https://wiki.call-cc.org/man/5/Types Chez instead provides typed/unchecke

It helps. Chicken seems to support exactly that: https://wiki.call-cc.org/man/5/Types https://wiki.call-cc.org/man/5/Types Chez instead provides typed/unchecked arithmetic functions, like fx+, flround and so on. In my experience, those sometimes make a big impact on performance(though realistically in some of those cases it would be better to ask C to do it for you). Racket similarly makes it possible to do either.