drop-while.clj

  (defn ^Observable drop-while
  [f ^Observable xs]
  (Observable/create (fn [^Observable subject]
                       (let [dropping (atom true)
                             subscription (subscribe* xs
                                                      (fn [v]
                                                        (when (or (not @dropping)
                                                                  (not (reset! dropping (boolean (f v)))))
                                                          (emit subject v)))
                                                      (fn [e] (error subject e))
                                                      (fn [] (done subject)))]
                         (Observable/createSubscription #(unsubscribe subscription))))))