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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Possible to recover default value of scalar type?
Date: Tue, 15 Dec 2020 11:30:31 +0200
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On 2020-12-15 3:27, Randy Brukardt wrote:
> "AdaMagica" <christ-usch.grein@t-online.de> wrote in message
> news:570e9d30-0b33-45f0-a9fe-163cc810a770n@googlegroups.com...
>> Dmitry A. Kazakov schrieb am Montag, 14. Dezember 2020 um 10:38:42 UTC+1:
>>> procedure Library_Foo (Bar : Baz := Baz'Default_Value)
>> Suppose type Baz has no default value aspect. Then a call Library_Foo
>> without parameter would use what?
>> A solution could be that the attribute is illegal if there is no aspect.
>> The compiler knows.
> 
> Not always. Never forget generics. One would hope to be able to use this on
> generic formal types, as most of them are going to have default values (at
> least in new code).


The generic formal type declarations could be extended to indicate that 
a Default_Value is required, for example:

    generic
       type T is private with Default_Value;

    ...