Re: Comments requested for a couple of Ada-Comments submissions

[Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP>]

On 2014-07-11, Niklas Holsti <niklas.holsti@tidorum.invalid> wrote:
> On 14-07-11 07:16 , Randy Brukardt wrote:
>> "Jeffrey Carter" <spam.jrcarter.not@spam.not.acm.org> wrote in message 
>> news:lpnb74$kmi$1@dont-email.me...
>> ...
>>> I don't see that there is anything here that the ARG would want to take 
>>> action on, especially given that Randy said they're only interested in 
>>> things that are hard or impossible to do in Ada. This is clearly not hard 
>>> or impossible.
>> 
>> Well, actually, I understand that a similar problem came up recently (I 
>> think it was related to SPARK) and that the GNAT people had already hacked 
>> an ugly solution to it. A language-based solution would be better, at least 
>> if it's not too expensive to implement.
>> 
>> After all, two independent problems that can be solved with a relatively 
>> simple new feature make that feature more compelling. In any case, it's 
>> certainly OK for Simon to submit the problem; I've seen a lot sillier ideas 
>> than this one.
>> 
>>                                    Randy.
>
> Thanks, Simon, for working up this proposal.
>

You are welcome.

> 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's only occurred to me just now while typing up this response, but
I can't see how it could possibly make a difference, even with
variant records.

However, I just thought I would ask the question anyway. :-)

>
> Furthermore, the proposal should IMO not be limited to record types. The
> same should be possible for array aggregates, as in this example:
>
>    type Month_Days is array (Month) of Positive;
>
>    Normal_Year_Days : constant Month_Days :=
>       (Jan => 31, Feb => 28, Mar => 31, ..., Dec => 31);
>
>    Leap_Year_Days : constant Month_Days :=
>       (Normal_Year_Days changing Feb => 29);
>

I can see what you are saying here. Let me have a think about it. :-)

Simon.

-- 
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
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