Re: Ada 0y wish list: "with private"

[Jeffrey Carter <jrcarter@acm.org>]

"Beard, Frank" wrote:
> 
> What I have
> long wished for is to be able to do the following:
> 
>    package A is
> 
>       type B is private;
> 
>    private
> 
>       type B;  -- If the completion is not here,
>                -- then it's deferred to the body
> 
>    end A;
> 
>    package body A is
> 
>       type B is ...;
> 
>    end A;
> 
> This would allow the separation of the spec and body without
> the bother of using an access type, and the associated dangling
> memory and garbage collection issues.

Yes, or even

package A is
   type B is private;
   -- operations on B
end A;

package body A is
   type B is ...;
end A;

I submitted this as a 9X revision request, but it was rejected on the
grounds that one can achieve the same effect with an access type:

package A is
   type B is private;
   -- operations on B
private
   type X;
   type Y is access all X;
   type B is new Finalization.Controlled with record
      Z : Y;
   end record;
   -- procedures Initialize, Adjust, and Finalize
end A;

However, this is qualitatively different. I want to be able to use B as
B, and not have to get into all the details of it actually being an
access type. Let the compiler deal with all that. I suppose this would
involve a certain amount of work for compiler developers for what such
developers see as a small gain.

-- 
Jeff Carter
"Sons of a silly person."
Monty Python & the Holy Grail