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From: "G.B." <bauhaus@notmyhomepage.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Q: Trouble creating array and discriminated type
Date: Mon, 23 Jan 2017 09:02:39 +0100
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Date: 2017-01-23T09:02:39+01:00
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On 21.01.17 18:05, Stephen Leake wrote:
>>   type Ephemeris_Data (Offset_Maximum, Record_Maximum : Positive) is tagged record
> If you add defaults to the discriminants, Ada will let you declare an uninitialized object.

Defaults for discriminants of tagged types would not be permitted,
only if objects of the type can not have their discriminants changed
after creation (tagged limited). The reason is stated in AARM 3.7(9.*)
and it seems to say "It's complicated".

The paragraph suggest that for some use cases, one can declare a subtype
that sets the discriminants to default values. IIUC, these subtypes
can then be used in derivations also.

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