+$ model [count=@ud]
+$ message %noop
+$ other-message %other
++ main (program init update view subs)
++ init |= input=@t ^- model [count=0]
++ update |= [event=other-message current=model]
  ?- event
    %other [current ~]
++ view |= state=model ^- (element message) (text "view")
++ subs |= state=model ^- (list (sub message)) ~