Simple first approach to a DAG

gistfile1.clj

(ns bayle.core
  (require clojure.set))

(defprotocol NODE
  (change [this key new-value])
  (add-parent [this new-parent])
  (add-non-descendent [this new])
  (node? [this])
  (add-chile [this child]))

(defprotocol DAG
  (add-node [this node])
  (remove-node [this node])
  (descendents [this node])
  (non-descendents [this node child]))

(defrecord Node [name table parents non-descendents child]
  NODE
  (node? [this]
    true)
  (change [this key new-value]
    (assoc this key new-value))
  (add-parent [_ new-parent]
    (Node. name table (clojure.set/union parents new-parent) non-descendents child))
  (add-non-descendent [_ new-non-des]
    (Node. name table parents (clojure.set/union non-descendents new-non-des) child))
  (add-child [_ new-child]
    (Node. name table parents non-descendents (clojure.set/union non-descendents new-child))))

(defn new-node
  [name & {:keys [table parents non-descendents child] :or {table {}
                                                            parents #{}
                                                            non-descendents #{}
                                                            child #{}}}]
  (Node. name table parents non-descendents child))

(extend-type clojure.lang.PersistentHashSet
  DAG
  (add-node [this node] ;; TODO CHECK EDGE
    {:pre [(node? node)]
     :post [(set? %)]}
    (conj this node))
  (descendents [this node]
    {:pre [(node? node)]
     :post [(set? %)]}
    (clojure.set/difference this (:non-descendents node)))
  (non-descendents [this node child]
    {:pre [(node? node) (node? child)]
     :post [(set? %)]}
    (clojure.set/difference this (clojure.set/union (map #(descendents this %) child)))))

(defn new-DAG []
  #{})