X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~mdw/git/jlisp/blobdiff_plain/ca5f00c8c447c05ab7d843a075bb68bc884fef47..a2e7266a20fff562054c0f546e4a49c03b93ce20:/queue.lisp

diff --git a/queue.lisp b/queue.lisp
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-;;; -*-lisp-*-
-;;;
-;;; A simple queue
-;;;
-;;; (c) 2008 Mark Wooding
-;;;
-
-;;;----- Licensing notice ---------------------------------------------------
-;;;
-;;; This program is free software; you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published by
-;;; the Free Software Foundation; either version 2 of the License, or
-;;; (at your option) any later version.
-;;;
-;;; This program is distributed in the hope that it will be useful,
-;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-;;; GNU General Public License for more details.
-;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program; if not, write to the Free Software Foundation,
-;;; Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
-
-(defpackage #:queue
-  (:use #:common-lisp)
-  (:export #:make-queue #:queue-emptyp #:enqueue #:dequeue))
-(in-package #: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
-  ;; in the queue, and the car points to the last entry in the list.  If the
-  ;; queue is empty, then the car points to the queue itself for the sake of
-  ;; uniformity.
-  (let ((q (cons nil nil)))
-    (setf (car q) q)))
-
-(defun queue-emptyp (q)
-  "Answer whether the queue Q is empty."
-  (null (cdr q)))
-
-(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)))
-
-(defun dequeue (q)
-  "Remove and return the object at the head of the queue Q."
-  (if (queue-emptyp q)
-      (error "Queue is empty.")
-      (let ((c (cdr q)))
-	(prog1 (car c)
-	  (unless (setf (cdr q) (cdr c))
-	    (setf (car q) q))))))
-
-#+ test
-(defun queue-check (q)
-  "Check consistency of the queue Q."
-  (assert (car q))
-  (if(null (cdr q))
-     (assert (eq (car q) q))
-     (do ((tail (car q))
-	  (collection nil (cons (car item) collection))
-	  (item (cdr q) (cdr item)))
-	 ((endp item) (nreverse collection))
-       (if (cdr item)
-	   (assert (not (eq item tail)))
-	   (assert (eq item tail))))))
-
-#+ test
-(defun test-queue ()
-  "Randomized test of the queue functions."
-  (let ((q (make-queue))
-	(want nil))
-    (dotimes (i 10000)
-      (case (random 2)
-	(0 (setf want (nconc want (list i)))
-	   (enqueue i q))
-	(1 (if (null want)
-	       (assert (queue-emptyp q))
-	       (progn
-		 (let ((j (dequeue q))
-		       (k (pop want)))
-		   (assert (= j k)))))))
-      (assert (equal want (queue-check q))))))
-
-;;;----- That's all, folks --------------------------------------------------
diff --git a/queue.lisp b/queue.lisp
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+lisp/queue.lisp
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