Om cursor protocol idea

cursor.cljs

(defprotocol ICursor
  (value [self] "Get the current value of the cursor")
  (transact [self f] "Update the current value of the cursor"))
  
(extend Atom
  ICursor
  (value [self]
    (deref self))
  (transact [self f]
    (swap! self f)))
    
(defrecord PathCursor [parent path]
  ICursor
  (value [self]
    (get-in (value parent) path))
  (transact [self f]
    (transact parent #(update-in % path f))))
    
(defn join [parent korks]
  (let [path (if (seq? korks) korks [korks])]
    (PathCursor. parent path)))
    
(defrecord RenameCursor [parent renames]
  ICursor
  (value [self]
    (rename (value parent) renames))
  (transact [self f]
    (transact parent (fn [state]
      (rename 
        (f (rename state renames))
        (map-invert renames))))))