Dijkstra's algorithm in clojure

dijkstra.clj

(defprotocol WEIGHTED_GRAPH
  (nodes [graph])
  (neighbors [graph node])
  (weight [graph from to]))

(defn dijkstra
  [start goal graph]
  (let [nodes (nodes graph)
        neighbors #(neighbors graph %)
        weight #(weight graph %1 %2)]
    (loop [dist (merge (into {} (for [x nodes] [x ##Inf]))
                       {start 0})
           unseen (into (priority-map) tentative-dist)
           visited? #{}
           path {}]
      (let [[best-unseen best-dist] (peek unseen)]
        (if (or (= best-dist ##Inf) ; no path from start to goal
                (visited? goal)
                (empty? unseen))
          (path goal)
          (let [closer-nbrs (for [nbr (neighbors best-unseen)
                                  :let [new-dist (+ best-dist
                                                    (weight best-unseen nbr))]
                                  :when (< new-dist (dist nbr))]
                              [nbr new-dist])
                closer-paths (for [[nbr _] closer-nbrs]
                               [nbr (conj (path best-unseen) nbr)])]
            (recur (into dist closer-nbrs)
                   (into (pop unseen) closer-nbrs)
                   (conj visited? best-unseen)
                   (into path closer-paths))))))))