Lisp isn't a functional language (in the sense that you appear to mean; it has functions as a first-class type, of course, but that's different). This code is

Lisp isn't a functional language (in the sense that you appear to mean; it has functions as a first-class type, of course, but that's different). This code is imperative: (tagbody start (decf x) (format t "~a~%" x) (when (plusp x) (go start))) Lisp works just fine in imperative contexts.