C++ Queues
  
  The C++ Queue is a container adapter that gives the programmer a
  FIFO (first-in, first-out) data structure.
  Display all entries for C++ Queues on one
  page, or view entries individually:
  
    
      | Queue constructor | 
      construct a new queue | 
    
    
      | back | 
      returns a reference to last element
      of a queue | 
    
    
      | empty | 
      true if the queue has no
      elements | 
    
    
      | front | 
      returns a reference to the first
      element of a queue | 
    
    
      | pop | 
      removes the top element of a
      queue | 
    
    
      | push | 
      adds an element to the end of the
      queue | 
    
    
      | size | 
      returns the number of items in the
      queue |