→ (defn real-foo [a] (bla a)) • if → cond • wrap in let, promote let • Namespaces, import • Refactoring • Simple: rename, replace function, change order • Complex: change flow, change data structure IDE level complexity Char editor (Notepad, DOS E) Text editor (vi, emacs, ed) Code editor (emacs, acme, vs code, sublime) Code editor + dev. env. (IDE) (emac/cider, IDEA/Cursive, Eclipse, Xcode, etc)