(defpackage #:queue
(:use #:common-lisp)
- (:export #:make-queue #:queue-emptyp #:enqueue #:dequeue))
+ (:export #:make-queue #:queue-emptyp #:enqueue #:pushqueue #:dequeue))
(in-package #:queue)
(defun make-queue ()
(setf (cdr (car q)) c
(car q) c)))
+(defun pushqueue (x q)
+ "Push the object X onto the front of the queue Q."
+ (let* ((first (cdr q))
+ (new (cons x first)))
+ (setf (cdr q) new)
+ (unless first (setf (car q) new))))
+
(defun dequeue (q)
"Remove and return the object at the head of the queue Q."
(if (queue-emptyp q)
(let ((q (make-queue))
(want nil))
(dotimes (i 10000)
- (case (random 2)
+ (case (random 3)
(0 (setf want (nconc want (list i)))
(enqueue i q))
- (1 (if (null want)
+ (1 (push i want)
+ (pushqueue i q))
+ (2 (if (null want)
(assert (queue-emptyp q))
(progn
(let ((j (dequeue q))