topo-sort.clj

(defn topo-sort
  "Provided a map of values to their dependencies, returns a seq of the values
  sorted topologically.
  Adapted from code by cgrande at:
  https://groups.google.com/forum/#!topic/clojure/-sypb2Djhio"
  [deps]
  (mapcat #(for [[u vs] %
                 :when (empty? vs)]
             u)
          (take-while seq
                      (iterate (fn [deps]
                                 (into {}
                                       (for [[u vs] deps
                                             :when (seq vs)]
                                         [u (mapcat deps vs)])))
                               deps))))