Lisp is not pure, in general. cons is "functional" because lists, if treated immutably, are functional. There's still setq (set! in Scheme), though, and operati

Lisp is not pure, in general. cons is "functional" because lists, if treated immutably, are functional. There's still setq (set! in Scheme), though, and operations on hash tables, arrays, and sets are typically mutating.