Re: Package's private parts and protected types

[Robert A Duff <bobduff@shell01.TheWorld.com>]

"Hibou57 (Yannick Duch�ne)" <yannick_duchene@yahoo.fr> writes:

> Synchronized-and-the-like interface types are limited, so the built-in-
> place is indeed really built-in-place (no kind of conversion allowed
> at any stage). The initializer function have to return a class wide
> and return it using an extended return statement which is required to
> return the same exact type/subtype as the one function returns.
>
> This way of doing thing is not compatible with the implementation-
> hiding requirement, as it would require the implementation type to be
> exposed in the public part, so that I could define a public function
> returning this exact type.

I don't understand the problem.  The following should work.
Doesn't it do what you want?  Type T exports Public,
but hides Hidden.  No heap allocation.

 package P is
    type T is synchronized interface;
    function Create return T'Class;

    procedure Public (X : in out T) is abstract;

 private

    protected type T2 is new T with
       overriding entry Public;
       entry Hidden;
    end T2;

 end P;

 package body P is
    function Create return T'Class is
    begin
       return Result : T2 do
          ...
       end return;
    end Create;

    protected body T2 is
       entry Public when ... is
       begin
          ...
       end Public;

       entry Hidden when ... is
       begin
          ...
       end Hidden;
    end T2;

 end P;

 with P; use P;
 procedure Main is

    X : T'Class := Create;

 begin
    Public (X);
 end Main;

- Bob