Clojure function that waits on the completion of another function before executing

hello.core> (def lock [])
#'hello.core/lock

hello.core> (def wait-for-function-helper             
              (memoize (fn [f args]
                         (let [answer (promise)]
                           (println "waiting for function " f " with args" args)
                           (future (deliver answer (apply f args)))
                           answer))))

#'hello.core/wait-for-function-helper
hello.core> (defn wait-for-function [& args]
              (locking lock
                (apply wait-for-function-helper args)))
#'hello.core/wait-for-function

hello.core> (defn dependent-func [f g & args]
              @(wait-for-function f args)
              (apply g args))
#'hello.core/dependent-func

hello.core> (defn slow-f-1 [x]
              (println "starting slow-f-1")
              (Thread/sleep 10000)
              (println "finishing slow-f-1")
              (dec x))
#'hello.core/slow-f-1

hello.core> (do (future
                  (println "first" (dependent-func slow-f-1 inc 4)))
                (future
                  (println "second" (dependent-func slow-f-1 inc 4))))

waiting for function  
#object[clojure.core$future_call$reify__6736 0x40534083 {:status :pending, :val nil}] with args (4)
#object[hello.core$slow_f_1 0x4f9b3396 hello.core$slow_f_1@4f9b3396]
starting slow-f-1
finishing slow-f-1
second
first
5
5

hello.core> (do (future
                  (println "first" (dependent-func slow-f-1 inc 4)))
                (future
                  (println "second" (dependent-func slow-f-1 inc 4))))

#object[clojure.core$future_call$reify__6736 0x3935ea29 {:status :pending, :val nil}]
first 5
second 5