using a var to count a callback

gistfile1.clj

;; the simple example:
(with-local-vars [foo 0] 
  (var-set foo (+ 1 (var-get foo)))
  (var-get foo))

;; the reason why - a call back
;; (this code still needs some cleaning)
;; the TupleQueryResultHandler is called once per result of the query
(defn sesame-visit-count-sparql [kb query-string]
  (with-local-vars [count 0]
    (.evaluate ^TupleQuery
               (.prepareTupleQuery ^RepositoryConnection (connection! kb)
                                   QueryLanguage/SPARQL
                                   query-string)
               (proxy [TupleQueryResultHandlerBase] []
                 (handleSolution [bindings]
                                 (var-set count 
                                          (+ 1 (var-get count))))))
    (var-get count)))