cont.clj

(defmacro return% [a]
  `(fn return-fn# [success# error#]
     #(try
        (success# ~a)
        (catch Throwable t#
          (error# t#)))))

(defn bind% [m b]
  (fn a [success error]
    #(m (fn x [value] ((b value) success error)) error)))

(defn try% [m handler]
  (fn [success error]
    (let [new-error (handler error)]
      #(m success new-error))))

(defmacro let% [bindings body]
  (if (seq bindings)
    (let [[name value & bindings] bindings]
      (if (= name '!)
        `(do ~value (let% ~bindings ~body))
        `(bind% ~value (fn bindfn# [~name] (let% ~bindings ~body)))))
    body))

(def call-cc% identity)

(trampoline
 (let% [[success error n] (call-cc% (fn [success error]
                                      (success
                                       [(fn [value] (return% (success value)))
                                        (fn [value] (return% (error value)))
                                        0])))
        _ (return% (prn n))]
   (if (> 10 n)
     (success [success error (inc n)])
     (return% nil)))
 identity
 prn)