I was (re-)reading On Lisp yesterday and came across two further variations by pg: In preface: As well as writing their programs down toward the language, exp

I was (re-)reading On Lisp yesterday and came across two further variations by pg: In preface: As well as writing their programs down toward the language, experienced Lisp programmers build the language up toward their programs. Then later in 1.2 "Programming Bottom-up", pg rephrases that statement: In Lisp, you don’t just write your program down toward the language, you also build the language up toward your program