With guile and Racket, a non-linear reverse! at the end of a map is as fast as doing a non-tail-recursive map. There are trade-offs for both. The TCO'd map is

With guile and Racket, a non-linear reverse! at the end of a map is as fast as doing a non-tail-recursive map. There are trade-offs for both. The TCO'd map is a lot faster to restore when using continuations, but is not multi-shot continuation safe.