Natools

     limited private;

   type Data_Access is access Held_Data;
   for Data_Access'Storage_Pool use Data_Pool;


   type Immutable_Reference is new Ada.Finalization.Controlled with private;
   pragma Preelaborable_Initialization (Immutable_Reference);

   function Create
     (Constructor : not null access function return Held_Data)
      return Immutable_Reference;
      --  Create a new held object and return a reference to it

   procedure Replace

      Process : not null access procedure (Object : in Held_Data));
      --  Call Process with the held object

   Null_Immutable_Reference : constant Immutable_Reference;


   type Reference is new Immutable_Reference with private;
   pragma Preelaborable_Initialization (Reference);

   function Update (Ref : in Reference) return Mutator;
   pragma Inline (Update);
      --  Return a ereferenciable mutable access to the held object

   procedure Update
     (Ref : in Reference;