Re: problem with abstract types

["Robert I. Eachus" <rieachus@attbi.com>]

Jeffrey Carter wrote:

> I'm going to risk making a donkey of Fred Bloggs and his brother and 
> guess that he really meant to type
> 
> Reg : Registry'Class := Open_Registry (...);

Oops!  Yep.

> I have used Open_Registry because that's the Ada Way :)

I was trying to not do too much of the Ada way and got burned!  I would 
normally do this:

  package Registries is
    type Registry is limited private;
    type Access_Mode is (User_Mode, Supervisor_Mode);
    function Open_Registry(Name: String; Mode: Access_Mode := User_Mode)
      return Registry;
private
    type Real_Registry(L: Natural) is tagged record
      Name: String(1..L);
      -- ...
    end record;
    type Registry is access Real_Registry'Class;
end Registries;

Actually, I'd probably go a bit further, and make Registry explicitly 
Controlled, to ensure that Registry objects were explicitly finalized. 
But that was definitely way out of bounds of this discussion.