package Linked_Lists is

   type Link is limited private;

   procedure Add (List   : in out Link;

                  Datum  : in Boolean);

   procedure Print_All (List: in Link);

   subtype List_Type is Link;

private

   type Node;

   type Link is access Node;

   type Node is record

      Datum  : Boolean;

      Next   : Link;

    --Prev   : Link;

   end record;

end Linked_Lists;

with Ada.Text_IO;

package body Linked_Lists is

   procedure Add (List   : in out Link;

                  Datum  : in Boolean) is

      Aux_Link : Link;

   begin

      Aux_Link := new Node;

      Aux_Link.Datum := Datum  ;

      Aux_Link.Next  := List;

      List := Aux_Link ;

   end Add;

   procedure Print_All (List: in List_Type) is

      Aux_Link : Link;

   begin

      Aux_Link := List;

      while Aux_Link /= null loop

         Ada.Text_IO.Put_Line (Boolean'Image(Aux_Link.Datum));

         Aux_Link := Aux_Link.Next;

      end loop;

   end Print_All;

end Linked_Lists;