Using atoms in Clojure

atoms_use.clj

;A map stored in an atom
(def register (atom {}))

;An item to register
(defrecord register-item [item-name time-added])

(defn addSomethingToRegister [item-name register]
  ;Do the following inside a let
  (let 
       ;create new register-item and assing to ref item
       [item (->register-item item-name (Date.))]
       ;create a new map by adding the new item to the existing register map
       ;use swap to replace the map inside the register atom
       (swap! register #(assoc % (:item-name item) item))
       ; return the created item - last expresion inside the let is always returned
       item))
     
;To use it
(addSomethingToRegister "1" register)

A little example of using atoms in clojure.