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From: Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP>
Newsgroups: comp.lang.ada
Subject: Re: Oberon and Wirthian languages
Date: Sat, 26 Apr 2014 17:15:09 +0000 (UTC)
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Date: 2014-04-26T17:15:09+00:00
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On 2014-04-26, Niklas Holsti <niklas.holsti@tidorum.invalid> wrote:
> On 14-04-26 09:19 , Georg Bauhaus wrote:
>> On 25/04/14 23:55, Randy Brukardt wrote:
>>> This is a case where the keyword will make all of the difference. If
>>> we were
>>> using a new keyword, perhaps something like:
>>>
>>>     A := (A replacing C => D, E => F);
>>>
>>> would do the trick.

As some other posters have said, I do think a unique keyword or attribute
would be required and I agree with you the actual choice of word matters.

>> 
>> Hasn't GNAT recently added something similar,
>> http://gcc.gnu.org/onlinedocs/gnat_rm/Attribute-Update.html#Attribute-Update

Thanks for the link; I had not come across this until now.

>
> Interesting. There does seem to be a need for this kind of thing, then.
>

Indeed. Once I started thinking in terms of aggregates I didn't know
about the above Update attribute and it only took me a few minutes to
come up with using the same attribute name on the LHS of an assignment.

For ACT to have added something similar would indeed seem to strongly
imply something like this is needed in Ada.

> However, the GNAT implementation does not allow changing discriminants,
> which was the main use-case that Randy told of in the Janus/Ada
> compiler. It seems a reasonable limitation to me.
>

I also would not have a problem with that limitation.

Simon.

-- 
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Microsoft: Bringing you 1980s technology to a 21st century world