Re: New aggregates with Ada 2022.

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 2022-06-22 01:39, Randy Brukardt wrote:
> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message
> news:t8qrmo$p79$1@gioia.aioe.org...
> ...
>> 1. Built-in operations -> hiding:
>>
>>     type T is private;
>>     function "+" (Left, Right : T) return T; -- Perfectly legal
>> private
>>     type T is range 1..100;
>>
>> 2. Primitive operations -> overriding.
> 
> BTW, these two are really the same thing. In the first example, the "+" is
> overriding the predefined operation.

Yes, they should be in a better world. A primitive operation is always 
reachable. The case above works differently from:

    type T is private;
    overriding
    function "+" (Left, Right : T) return T is abstract;

But this is a deeper problem of having such operations primitive.

> But note an important difference here from the aggregate case: in no case is
> an operation available for the private type that is *not* available for the
> full view. Since the syntax and semantics of container aggregates and array
> aggregate are subtly different (they are as close as we could make them, but
> that is not that close), there definitely are things that would be only
> possible when written for the private view. That would be new for Ada. So
> while a definition could be made, it would be confusing in some cases. And
> this case isn't useful enough to make that effort.

Much could be resolved by attributing proper types to all assumed or 
real intermediate steps:

    type T is private;
    function "+" (Left, Right : T) return T;
private
    type T_Parent is range 1..100;
    type T is new T_Parent;

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de