I think they're referring to the Racket programming language [0]. Shriram also authored "Programming Languages: Application and Interpretation" [1] and co-auth

I think they're referring to the Racket programming language [0]. Shriram also authored "Programming Languages: Application and Interpretation" [1] and co-authored "How to Design Programs" [2] with Matthias Felleisen, Robby Findler, and Matthew Flatt. Both books use Racket as a base (well, PLAI uses PLAI/typed, which is built from Racket and utilized the DrRacket interpreter... close enough). [0] https://racket-lang.org https://racket-lang.org [1] http://cs.brown.edu/~sk/Publications/Books/ProgLangs/ http://cs.brown.edu/~sk/Publications/Books/ProgLangs/ [2] http://www.htdp.org http://www.htdp.org