Queue

A queue is a data structure that allows insertion and retrieval of data in the FIFO manner, i.e. the first-in first-out order. Since the queue class is defined by extending the cons class, ordinary list functions can be applied to a queue. For example, caar retrieves the next element to be dequeued, and cadr gets the element that is queued most recently.

queue [class]

  :super   cons 

  :slots 		 (car cdr) 

defines queue (FIFO) objects.

:init [method]

initializes the queue to have no elements.

:enqueue val [method]

puts val in the queue as the most recent element.

:dequeue &optional (error-p nil) [method]

retrieves the oldest value in the queue, and removes it of the queue. If the queue is empty, it reports an error when error-p is non-nil, or returns NIL otherwise.

:empty? [method]

returns T if the queue is empty.

:length [method]

returns the length of the queue.