(defvar relops '(#\= #\< #\> (#\< #\>) (#\< #\=) (#\> #\=))) ; instance variables for the relational operators
(defvar literals '((#\t #\r #\u #\e) (#\f #\a #\l #\s #\e))) ; boolean literals
(defvar letters '(#\a #\b #\c #\d #\e #\f #\g #\h #\i #\j #\k #\l #\m #\n #\o #\p
          #\q #\r #\s #\t #\u #\v #\w #\x #\y #\z #\A #\B #\C #\D #\E #\F #\G #\H
          #\I #\J #\K #\L #\M #\N #\O #\P #\Q #\R #\S #\T #\U #\V #\W #\X
          #\Y #\Z)) ;list of letters
(defvar digits '(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9)); list of digits
(defvar whitespace '(#\Tab #\Linefeed #\Return #\Space))
(defvar input '(#\t #\r #\u #\e #\^))
(defvar cur ()) ;global variable to hold current token
(defun main ()
  (format t "Entering <bool_expr>~%")
  (print (expr)))
(defun expr ()
  (progn
    (reload)
    (format t "Entering <and_term>~%")
    (cond ((equal (first cur) #\|)
       (progn
         (pop input)
         (reload)
         (return-from expr(expr))))
      ((equal input nil)
       t)
      (t nil)))
  (term))
(defun term ()
  (format t "Entering <bool_factor>~%")
  (return-from term (factor))
  (if (equal (first cur) #\&)
      (progn (pop input)
         (print "&")
         (reload)
         (format t "Entering <bool_factor>~%")
         (factor))))


(defun factor ()
  (cond ((member cur literals :test 'equal)
     (return-from factor (literal)))
    ((equal (first cur) #\!)
     (progn (pop cur)
        (return-from factor (literal))))
    ((or (member (first cur) letters) (member (first cur) digits))
     (progn
       (format t "Entering <relation_expr>~%")
       (return-from factor (relation))))
    (t (return-from factor nil))))

(defun literal ()
  (format t "Entering <bool_literal>~%")
  (setf cur ()));empties the list so we can fill it with more of the expression

(defun relation ()
  (if (member (first cur) relops)
      (progn (relop)
         (reload)
         (cond ((id)
            (id))
           (t (return-from relation nil)))))
  (id))



(defun id ()
  (if (equal cur nil)
      (return-from id nil))
  (format t "Entering <id>")
  (loop for c in cur do
       (if (not (or (member c letters) (member c digits)))
       (return-from id nil)))
  (reload)
  t)


(defun relop ()
  (format t "Entering <relop>~%"))

(defun reload ()
  (setf cur ())
  (loop for c in input until (member c whitespace) do
       (setf cur (append cur (list c)))
       (pop input))
  (pop input))


(main)