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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Ada.Real_Time.Time_Last
Date: Sat, 18 Nov 2017 19:31:37 +0200
Organization: Tidorum Ltd
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Xref: feeder.eternal-september.org comp.lang.ada:48992
Date: 2017-11-18T19:31:37+02:00
List-Id: <comp.lang.ada>

On 17-11-18 18:01 , Dmitry A. Kazakov wrote:
> On 2017-11-18 16:24, Niklas Holsti wrote:
>
>> Making Count'First and Count'Last available is part of the goal of the
>> extension, but the point is that the *expressions* that define their
>> values would still be *private*, which means that the user of the type
>> cannot (or is not meant to) depend on those expressions. The user can
>> access the end result ('First, 'Last) but is not meant to depend on
>> any other properties of those expressions.
>
> The proposal should also encompass other cases where information hiding
> principle gets violated, e.g.:
>
>    procedure Foo (I : Integer := 20);
>
> If I don't want to expose the default or when the parameter is a private
> type, I should be able to provide a private value, just like in your case:
>
>    type Count is range 0..<private-value>;
>
> Same applies to the defaults of record type members, BTW.

Those privacy needs can already be handled by defining the relevant 
values as deferred constants (perhaps modulo some freezing-point 
concerns). Of course this method means that the private constant must be 
given a name; that name may or may not be useful, depending on the case.

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