core.clj

(ann get-from-state
     (t/All [a b]
            [(t/Option (t/Map b a)) (t/Option (t/Coll b)) -> (t/Option a)]))
(defn get-from-state [state keys]
  (t/loop [acc :- (t/Option a) nil
           keys :- (t/Option (t/Coll b)) keys]
    (if-not (and state (seq keys))
      acc
      (recur (get state (first keys))
             (rest keys)))))


(ann get-from-state2
     [(t/Option (t/Map t/Any t/Any))
      (t/Option (t/Coll t/Any)) -> (t/Option t/Any)])
(defn get-from-state2 [state keys]
  (t/loop [acc :- (t/Option Any) nil
           keys :- (t/Option (t/Coll t/Any)) keys]
    (if-not (and state (seq keys))
      acc
      (recur (get state (first keys))
             (rest keys)))))

(ann get-from-state-orig
     [(U t/Any (t/Map t/Any t/Any))
      (t/Option (t/Coll t/Any)) -> (t/Option t/Any)])
(defn get-from-state-orig [state keys]
  (if (or (nil? state) (empty? keys) (not (map? state)))
    state
    (recur (get state (first keys))
           (rest keys))))