;; make sure t 'contains' everything in l.
;; this returns a list of the elements #t if the
;; element is in the tree and the element number
;; if the element is missing.
(define (check-contents t l)
   (map (lambda (val) 
        (if (contains t val) 
            #t
            val
        ) 
     )
     l
   )
)

;; this prints out a message followed by an object value.
(define (print message value)
   (display ";  ")
   (display message)
   (write value)
   (newline)
)


;; initial elements to add to tree.
(define el '(11 5 2 7 15 13 19))
 
;; create complete tree:
;;                   11
;;               5       15
;;             2   7   13  19
(define t (tree-add-list '() el))

(newline)
(newline)

;; make sure t contains everything.
(display ";; make sure t contains everything ")
(display "-- this checks add.\n") 
(print "el => " el)
(print "t => " t)
(print "(check-contents t el) => " (check-contents t el))
(newline)

;; delete 13.
(define t-13 (delete t 13))
(check-contents t-13 el)
(display ";; remove 13 from t ") 
(display "-- this checks delete on a leaf\n")
(print "t-13 => " t-13)
(print "(check-contents t-13 el) => " (check-contents t-13 el))
(newline)

;; delete 15 (in addition to 13)
(define t-13-15 (delete t-13 15))
(display ";; remove 13 from t-15 ")
(display "-- this checks delete on a node with only one child\n")
(print "t-13-15 => " t-13-15)
(print "(check-contents t-13-15 el) => " (check-contents t-13-15 el))
(newline)

;; delete 5 (from original tree)
(define t-5 (delete t 5))
(display ";; remove 5 from t ")
(display "-- this checks delete on a node with two children\n")
(print "t-5 => " t-5)
(print "(check-contents t-5 el) => " (check-contents t-5 el))
(newline)

;; delete 11 (root) from original tree
(define t-11 (delete t 11))
(display ";; remove 11 from t ")
(display "-- this checks delete of root\n")
(print "t-11 => " t-11)
(print "(check-contents t-11 el) => " (check-contents t-11 el))
(newline)

;; see if t contains any old element that is not in t.
(display ";; check to see if t contains 99\n")
(print "(contains t 99) => " (contains t 99))

;; by now, we should be pretty convinced 
;; that all of the tree functions work.
(newline)
(newline)