Simplified AST processing code from CinC

gistfile1.txt

(use '[clojure.walk :only [walk]])

(def ^:dynamic ^:private *frame*)
(defn- new-frame [] (atom {}))

(defn- collect-frame [ast]
  (case (:op ast)
    :constant
    {:constants [{:value (:form ast)}]}

    nil))

(defn- new-frame? [form]
  (#{:fn } (:op form)))

(defn- unboxed-parent? [ast] (#{:let} (:op ast)))
(def ^:dynamic *unbox* false)
(defn- process-frames-helper [f ast]
  (let [pre-fn
       (fn [form]
          (process-frames-helper f (if (:op form) (assoc form :unbox *unbox*) form)))
        post-fn
        (fn [form]
          (swap! *frame* (partial merge-with (comp vec distinct concat)) (f form))
          form)
        main
        (fn [f ast]
          (if (new-frame? ast)
            (binding [*frame* (new-frame)]
              (let [res (walk pre-fn post-fn ast)]
                (merge res @*frame*)))
            (walk pre-fn post-fn ast)))]
    (if (unboxed-parent? ast)
      (binding [*unbox* true] (main f ast))
      (main f ast))
    ))

(defn process-frames [ast]
  (binding [*frame* (new-frame)]
    (merge (process-frames-helper collect-frame ast) @*frame*)))

A vastly simplified example:

(process-frames {:op :fn :children [{:op :let :children [{:op :constant :form 1}]}]})

{:op :fn,
:constants [{:value 1}],
:children [
{:op :let,
:unbox false,
:children [
{:unbox true, :form 1, :op :constant}]}]}