X-Git-Url: https://git.distorted.org.uk/~mdw/lisp/blobdiff_plain/2626af6648d844d428b3da1c12d1401e42405593..3dba250d40912df843708c98114a084c731f4132:/queue.lisp

diff --git a/queue.lisp b/queue.lisp
index 03de433..44ec534 100644
--- a/queue.lisp
+++ b/queue.lisp
@@ -22,10 +22,10 @@
 ;;; Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 
 (defpackage #:queue
-  (:use #:common-lisp)
-  (:export #:make-queue #:queue-emptyp #:enqueue #:dequeue))
+  (:use #:common-lisp))
 (in-package #:queue)
 
+(export 'make-queue)
 (defun make-queue ()
   "Make a new queue object."
   ;; A queue is just a cons cell.  The cdr is the head of the list of items
@@ -35,16 +35,27 @@
   (let ((q (cons nil nil)))
     (setf (car q) q)))
 
+(export 'queue-emptyp)
 (defun queue-emptyp (q)
   "Answer whether the queue Q is empty."
   (null (cdr q)))
 
+(export 'enqueue)
 (defun enqueue (x q)
   "Enqueue the object X into the queue Q."
   (let ((c (cons x nil)))
     (setf (cdr (car q)) c
 	  (car q) c)))
 
+(export 'pushqueue)
+(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))))
+
+(export 'dequeue)
 (defun dequeue (q)
   "Remove and return the object at the head of the queue Q."
   (if (queue-emptyp q)
@@ -74,10 +85,12 @@
   (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))