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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Comments requested for a couple of Ada-Comments submissions
Date: Sat, 12 Jul 2014 08:52:48 +0300
Organization: Tidorum Ltd
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Xref: news.eternal-september.org comp.lang.ada:20887
Date: 2014-07-12T08:52:48+03:00
List-Id: <comp.lang.ada>

On 14-07-11 23:02 , Simon Clubley wrote:
> On 2014-07-11, Niklas Holsti <niklas.holsti@tidorum.invalid> wrote:
>> I think that this proposal should not be limited to solving the "update
>> of atomic" problem. The ability to write an aggregate that generates a
>> composite value by giving new values for just some of the components of
>> an existing composite value is quite useful in any context where a
>> composite value is used.
>>
> 
> That is a very good point. I will add wording that makes it clear the
> exact same syntax could be used for general updating of, say, records
> in general.
> 
> It does raise another point, however. So far, I have only thought about
> non-discriminated records due to my focus on device registers. Are
> there any additional issues when discriminated records are involved ?

It seems to me that the legality and semantics of a partial aggregate
are easily defined by treating the partial aggregate as a syntactic
abbrevation of the corresponding full aggregate, that is, as syntactic
sugar. This should work even if some of the components named in the
partial aggregate are discriminants.

The only additional dynamic semantics to be defined are the indivisible
read ("as a whole") of an atomic object and the single read of a
volatile object, as you already have written in your proposal.

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