Correct, HN is written in Arc, a dialect of Lisp. But, the Arc compiler is written in Racket[1], and internally outputs Racket code[2]. "mzscheme"[3] is an ear

Correct, HN is written in Arc, a dialect of Lisp. But, the Arc compiler is written in Racket[1], and internally outputs Racket code[2]. "mzscheme"[3] is an early version of PLT Scheme, aka Racket. [1] https://github.com/arclanguage/anarki/blob/master/ac.scm https://github.com/arclanguage/anarki/blob/master/ac.scm [2] http://arclanguage.org/item?id=14608 http://arclanguage.org/item?id=14608 [3] http://docs.racket-lang.org/mzscheme/ http://docs.racket-lang.org/mzscheme/