GraphML target update

graphml.clj

(def mytestxml
  "<graphml>
<graph edgedefault='directed'>
<node id='n1' />
<node id='n2' />
<node id='n3' />
<node id='n4' />
<edge id='e1' source='n1' target='n3' />
<edge id='e2' source='n2' target='n3' />
</graph>
</graphml>")
      
(def mytest (clojure.xml/parse (java.io.ByteArrayInputStream. (.getBytes mytestxml))))

(require '[clojure.zip :as zip]
         '[clojure.contrib.zip-filter.xml :as zf])

(defn edit-target
  "Edit target attribute of a GraphML edge"
  ([new-target]
     (fn [node] (edit-target node new-target)))
  ([node new-target]
     (assoc node
       :attrs
       (assoc (:attrs node) :target new-target))))

;;; Code below doesn't work: returns a list of xml struct-maps
;;; where one n3 target is changed to n4 target
;;; Also returns empty list if no n3 target found
(defn update-edges
  "Update edge targets from old-target to new-target"
  [root old-target new-target]
  (zf/xml-> (zip/xml-zip root)
            :graph
            :edge
            (zf/attr= :target old-target)
            #(zip/edit % edit-target new-target)
            zip/root))