1. -- 
  2. -- Uwe R. Zimmer, Australia, 2015 
  3. -- 
  4.  
  5. generic 
  6.  
  7.    type Element is private; 
  8.  
  9. package Queue_Pack_Abstract is 
  10.  
  11.    type Queue_Interface is synchronized interface; 
  12.  
  13.    procedure Enqueue (Q : in out Queue_Interface; Item :     Element) is abstract; 
  14.    procedure Dequeue (Q : in out Queue_Interface; Item : out Element) is abstract; 
  15.  
  16. end Queue_Pack_Abstract;