streams.clj

(defn rich-stream*
  [name state-thunk f]
  (println name)
  (println "State:" @state/streams)
  (if-let [warm-state (get @state/streams name)]
    (do (println "Using warm-state:" warm-state)
        (f warm-state))
    (let [state (state-thunk)]
      (do (println "Using cold state:" state)
          (swap! state/streams assoc f state)
          (f state)))))

(defmacro rich-stream
  [state-thunk f]
 `(rich-stream* (list 'quote ~f) ~state-thunk ~f))