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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Array of records with default values not propagating to array
Date: Sun, 4 Feb 2018 11:21:36 +0200
Organization: Tidorum Ltd
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Xref: reader02.eternal-september.org comp.lang.ada:50296
Date: 2018-02-04T11:21:36+02:00
List-Id: <comp.lang.ada>

On 18-02-03 17:26 , Simon Wright wrote:

> I find that
>
>    type Card_Info (Trump : Boolean := False) is record
>       Name : Ada.Strings.Unbounded.Unbounded_String;
>       Divinatory_Meaning : Ada.Strings.Unbounded.Unbounded_String;
>       ...
>
>          TDeck (Index) :=
>            (Trump       => True,
>             Trump_Value => Index_1,
>             others      => <>);
>          ...
>
>             TDeck (Index) :=
>               (Trump      => False,
>                Card_Value => Card_Index,
>                Suit_Value => Suit_Index,
>                others     => <>);
>
> compiles OK and seems to run perfectly well. Presumably this is OK
> because the initial value for an otherwise-uninitialized unbounded
> string is the empty string. Or maybe it's GNAT being over-helpful, since
> it seems not to obey ARM 4.3.1(17.1)[1].
>
> [1] http://www.ada-auth.org/standards/rm12_w_tc1/html/RM-4-3-1.html#p17.1

I don't think that ARM paragraph applies to the "others" in this code. 
The paragraph says:

"A record_component_association for a discriminant without a 
default_expression shall have an expression rather than <>"

but the components covered by the "others" in this code are not 
discriminants. The discriminant is the Trump component, and the 
associations for Trump have an expression (True or False), not <>.

(Moreover, the Trump component has a default expression (False), which 
makes ARM 4.3.1(17.1) inapplicable even to "Trump => <>".)

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
       .      @       .