Re: Extending discriminant types

[anon@anon.org (anon)]

--
--  Compiles and Runs using GNAT 3.15p
--
--  This works in Ada 95 compilers because all types including a tag type 
--  has a discriminant value of at least 2 aka itself and Null. And that 
--  suggest that ALL types have a constraint of at least two. 
--
procedure V is

    type Point is tagged record
                           X : Float := 0.0 ;
                           Y : Float := 0.0 ;
                         end record ;
    type Point_Acesss is access all Point'Class ;

    type D is new Point with record
                           Z : Float := 0.0 ;
                         end record ;

    type E is new D with null record;
 
    Var : Point_Acesss ;

begin -- V
  Var := new E'Base ;
end V ;

In <49254e2d$0$30232$9b4e6d93@newsspool1.arcor-online.net>, Georg Bauhaus <rm.dash-bauhaus@futureapps.de> writes:
>Georg Bauhaus schrieb:
>> Ludovic Brenta schrieb:
>>> On Nov 20, 9:30 am, christoph.gr...@eurocopter.com wrote:
>>>> On 20 Nov., 08:21, a...@anon.org (anon) wrote:
>>>>
>>>>> Since, the orginal post suggest that the poster was using GNAT Ada 95
>>>>> compiler. Because the poster states that he can compiler the code. So,
>>>>> I used Gnat 3.15p using Ada 95 specs.
>>> One can also try GNAT GPL Edition 2008 or GCC 4.3 (or even 4.4) and
>>> pass it the -gnat95 option which is documented in the Secret GNAT
>>> User's Guide.
>> 
>> GNAT has -gnat83 as well, but rejects, too, because there are
>> neither tagged nor abstract types in Ada 83.
>> 
>> Just out of curiosity, given
>> 
>>    type T is tagged ...;
>>    type D is new T with ...;
>>    type E is new D with ...;
>> 
>> what would E'Base be?
>> 
>> Assuming that D is privately tagged, would E'Base
>> have different effects depending on whether E's tag
>> is visible or not?
>
>D's tag, ie.