COMMENT ⊗   VALID 00002 PAGES
C REC  PAGE   DESCRIPTION
C00001 00001
C00002 00002	Problem 5.
C00003 ENDMK
C⊗;
Problem 5.

(defun insert (x q)
       (prog (tem)
	     (setq tem (list x))
	     (if (null (car q))
		 (return (cons tem tem)))
	     (setf (cddr q) tem)
	     (setf (cdr q) tem)
	     (return q)))

(defun remove (q)
       (if (null (car q))
	   nil
	   (prog (tem)
		 (setq tem (list (caar q)))
		 (setf (car q) (cdar q))
		 (if (null (car q)) (setf (cdr q) nil))
		 (return tem))))

(setq q1 '(nil))
(remove q1)
(setq q1 (insert 'a q1))
(setq q1 (insert 'b q1))
(remove q1)
q1
(remove q1)
q1
(remove q1)