; COSC 152
; Fall 2005
; Dennis Brylow
;
; Lecture 8 Demo
; Binary Tree using the define-datatype syntax extension.

(define-datatype tree tree?
                (tree-node
                 (datum number?)
                 (left tree?)
                 (right tree?))
                (tree-null))

(define add-tree
  (lambda (n t)
    (if (tree? t)
        (cases tree t
          (tree-null () (tree-node n t t))
          (tree-node (datum left right)
                     (if (< n datum)
                         (tree-node datum
                                    (add-tree n left)
                                    right)
                         (tree-node datum
                                    left
                                    (add-tree n right))))
          )
        'error-not-tree)
    )
  )

(define search-tree
  (lambda (n t)
    (if (tree? t)
        (cases tree t
          (tree-null () #f)
          (tree-node (datum left right)
                     (cond
                       ((eq? n datum) #t)
                       ((< n datum) (search-tree n left))
                       (else (search-tree n right)))))
        'error-not-tree)
    )
  )