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From: Blady <p.p11@orange.fr>
Newsgroups: comp.lang.ada
Subject: Re: Aggregate with derived types.
Date: Fri, 15 Sep 2023 09:27:57 +0200
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Le 14/09/2023 à 23:37, Jeffrey R.Carter a écrit :
> On 2023-09-14 22:00, Blady wrote:
>>
>> I wonder why the float list aggregate isn't inferred by the compiler 
>> and need some help with a qualification.
> 
> I'm not sure. But can't you simply write
> 
> ML2 : My_Float_List2 := [-3.1, -6.7, 3.3, -3.14, 0.0];
> 
> ? I presume that My_Float_List2 inherits its aggregate definition from 
> My_Float_List1.

Unfortunately not directly:
     10.    ML2c : My_Float_List2 := [-3.1, -6.7, 3.3, -3.14, 0.0];
                                     |
         >>> error: type of aggregate has private ancestor "Vector"
         >>> error: must use extension aggregate

Shouldn't inherit them?

Indeed you have it if you defined a private extension with explicit aspects:
    package PA is
       type My_Float_List3 is new My_Float_Lists.Vector with private with
         Constant_Indexing => Constant_Reference,
         Variable_Indexing => Reference,
         Default_Iterator => Iterate,
         Iterator_Element  => Float,
         Aggregate         =>
          (Empty => Empty, Add_Unnamed => Append, New_Indexed => 
New_Vector, Assign_Indexed => Replace_Element);
       function Constant_Reference
         (Container : aliased My_Float_List3; Index : Positive) return 
My_Float_Lists.Constant_Reference_Type is
         (My_Float_Lists.Constant_Reference (My_Float_Lists.Vector 
(Container), Index));
       function Reference (Container : aliased in out My_Float_List3; 
Index : Positive) return My_Float_Lists.Reference_Type is
         (My_Float_Lists.Reference (My_Float_Lists.Vector (Container), 
Index));
    private
       type My_Float_List3 is new My_Float_Lists.Vector with null record;
    end PA;

    ML3 : PA.My_Float_List3 := [-3.1, -6.7, 3.3, -3.14, 0.0];