(defstruct node :letter :ends-word :connections)

(defn new-node
  ([letter ends-word] (new-node letter ends-word '()))
  ([l e c] (struct-map node :letter l :ends-word e :connections c)))

(defn get-link [from letter]
  (filter (fn [c] (= (:letter c) letter))
          (:connections from)))

(defn add-link [node-target letter ends-word]
  (assoc node-target :connections
         (conj (:connections node-target)
               (new-node letter ends-word))))

(def testa (add-link (new-node 'a' false) 't' true))
(println (get-link testa 't'))