anchor.diff:  ;; ==> on-end
   ----
   
  +
   === Zip
   
   This combinator combines two observable sequences in one.
  
positive.code: 
  [source,clojure]
  ----
  [funcool/beicon "2.8.0"]
  ----
  
  
  
negative.code: [source, clojure]
  ----
  (def stream
    (rx/create (fn [sink]
                 (sink 1)          ;; next with `1` as value
                 (sink (rx/end 2)) ;; next with `2` as value and end the stream
                 (fn []
                   ;; function called on unsubscription
                   ))))
  