macroexpand-scan / macroexpand-reductions

gistfile1.clj

(defn macroexpand-scan
  ([form]
    (macroexpand-scan form []))
  ([form results]
    (let [expanded (macroexpand-1 form)]
      (if (= expanded form)
        results
        (recur expanded (conj results expanded))))))

;; Example

(defmacro a [s] `(defn ~(symbol s) [] ~s)) 

(macroexpand-scan `(a "f"))
; => [(clojure.core/defn f [] "f") 
;     (def f (clojure.core/fn ([] "f")))]
   

Seems like this is a special case of something you might call steady-state: apply function f repeatedly, like iterate does, but stopping when you get a repeated value. Then (macroexpand-scan form) is just (steady-state macroexpand-1 form). As a bonus, (macroexpand form) is (last (steady-state macroexpand-1 form)).

Nice! Love the way you identified the higher-order function latent within this function. I think that's a great way to look at Clojure, always trying to extract out the higher order function in things, makes everything uber-composable. Thanks. See: https://gist.github.com/1501358 , (def macroexpand-scan (partial steady-state macroexpand-1))