procedure Traverse (Tree  : in out Tree_Type;
                       Order : in Traversal_Order) is

      x:Integer:=1;

      procedure Checked_Process (Element: in out Element_Type) is
         New_Element: Element_Type := Element;
      begin
         Process (New_Element);
         if Key_Of (Element) /= Key_Of (New_Element) then
            Put("No value found!");
            raise No_Key;
         else
            Element := New_Element;
         end if;
      end Checked_Process;

     procedure MAX (Element: in out Element_Type) is
         New_Element: Element_Type := Element;
      begin
         if x=1 then
            Process (New_Element);
            x:=0;
         end if;
         if Key_Of (Element) /= Key_Of (New_Element) then
            Put("No value found!");
            raise No_Key;
         else
            Element := New_Element;
         end if;
      end MAX;

           procedure MIN (Element: in out Element_Type) is
         New_Element: Element_Type := Element;
      begin
         if x=0 then
            Process (New_Element);
            x:=1;
         end if;
         if Key_Of (Element) /= Key_Of (New_Element) then
            Put("No value found!");
            raise No_Key;
         else
            Element := New_Element;
         end if;
      end MIN;


      procedure Inorder (Tree : in Tree_Type) is
      begin
         if Tree /= null then
            --Put_Line(Retrieve(Tree, Integer));
            Inorder (Tree => Tree.Left);    -- Traverse Left subtree
            Checked_Process (Tree.Info);
            Inorder (Tree => Tree.Right);   -- Traverse Right subtree
         end if;
      end Inorder;

      procedure Preorder (Tree : in Tree_Type) is
      begin
         if Tree /= null then
            Inorder (Tree => Tree.Left);    -- Traverse Left subtree
            MIN (Tree.Info);
            Inorder (Tree => Tree.Right);--Traverse Right subtree
         end if;
      end Preorder;

      procedure Postorder (Tree : in Tree_Type) is


      begin
         if Tree /= null then
            Inorder (Tree => Tree.Right);  -- Traverse Left subtree
            MAX (Tree.Info);
            Inorder (Tree => Tree.Left);  -- Traverse Right subtree
         end if;
      end Postorder;

   begin -- Traverse
      case Order is
         when Inorder   => Inorder (Tree);
         when Preorder  => Preorder (Tree);
         when Postorder => Postorder (Tree);
      end case;
   end Traverse;