Racket! This is the language that the common author (Dr. Daniel Friedman) uses, ...

Racket! This is the language that the common author (Dr. Daniel Friedman) uses, and many of the Little books use custom DSLs implemented in Racket.

Racket now runs on Chez under the hood (inheriting the performance), and has a pretty decent ecosystem as far as schemes go.

(I TA for Dr. Friedman’s programming languages course)