package body List_Polymorphic_Cntl.Iterators is

procedure Null_Proc (Object  : in out Holder_Class_Ptr;
                     Continue: in out boolean) is
   begin -- Null_Proc
      null;
   end Null_Proc;
   ------------------------------------------------
procedure Front_To_Rear (List   : in     List_Type;
                         Process:        Process_Type) is
   begin -- Front_To_Rear
      Round_Trip (List, Process, Null_Proc'Access);
   end Front_To_Rear;
   ------------------------------------------------
procedure Rear_To_Front (List   : in     List_Type;
                         Process:        Process_Type) is
   begin -- Rear_To_Front
      Round_Trip (List, Null_Proc'Access, Process);
   end Rear_To_Front;
   ------------------------------------------------
procedure Round_Trip (List     : in     List_Type;
                      Down_Proc,
                      Up_Proc  :        Process_Type) is
   Continue: boolean := true;
   Next_One: Holder_Class_Ptr;
   procedure Rec_Iter (Point : in out Holder_Class_Ptr) is
      begin -- Rec_Iter
         if Point /= null then
             Next_One:= Point.Next;
             Down_Proc (Point, Continue);
             Point.Next:= Next_One;
             if Continue then
                 Rec_Iter (Point.Next);
                 if Continue then
                     Next_One:= Point.Next;
                     Up_Proc (Point, Continue);
                     Point.Next:= Next_One;
                 end if;
             end if;
         end if;
      end Rec_Iter;
      ---------------------------------------------
   begin -- Round_Trip
      Rec_Iter (List.Actual.all);
   end Round_Trip;
   ------------------------------------------------
end List_Polymorphic_Cntl.Iterators;