seven languages in seven weeks: clojure day 3

accounts.clj

(def accounts (ref []))

(defn openaccount [] (dosync (alter accounts conj 0)))
(defn debit [ accountnr debitammount] (dosync (alter accounts #(assoc %1 accountnr (- (get %1  accountnr) debitammount)))))
(defn credit [ accountnr creditammount] (dosync (alter accounts #(assoc %1 accountnr (+ creditammount (get %1  accountnr) )))))

(openaccount)
(println @accounts)
(credit 0 100)
(println @accounts)
(credit 0 100)
(println @accounts)

(println @accounts)
(debit 0 100)

(println @accounts)

barber.clj

(def waiting-customers (atom 0))
(def waiting-room-size 3)
(def number-of-haircuts (atom 0))

(def open? (atom true))

(defn open-shop [duration]
  (future
      (println "opening shop")
      (Thread/sleep (* 1000 duration ))
      (swap! open? not)
      (println "closing shop")
  )
)

(defn spawn-customers []
  (future
    (while @open?
      (if ( < @waiting-customers waiting-room-size )
        (do
           (println "entering")
           (swap! waiting-customers inc)
           (Thread/sleep (+ 10 (rand-int 20)))
        )
      )
    )
  )
)

(defn gotowork []
  (future
    (while @open?
      (if (> @waiting-customers 0 )
        (do
          (println "cutting")
          (swap! waiting-customers  dec)
          (swap! number-of-haircuts inc)
          (Thread/sleep 20)
        )
      )

    )
  )
 )

(def shopthread (open-shop 10))
(spawn-customers )
(gotowork)
(deref shopthread )
(println @number-of-haircuts)