From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Interesting article on ARG work
Date: Tue, 10 Apr 2018 10:17:56 +0200
Date: 2018-04-10T10:17:56+02:00 [thread overview]
Message-ID: <pahrvj$1hhm$1@gioia.aioe.org> (raw)
In-Reply-To: pagi68$ptq$1@franka.jacob-sparre.dk
On 09/04/2018 22:24, Randy Brukardt wrote:
> Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message
> news:pag4fd$pn4$1@gioia.aioe.org...
>> On 2018-04-09 18:12, Niklas Holsti wrote:
>>
>>> For example, the text
>>>
>>> if Foo then
>>> Bar;
>>> @ else
>>> @ Baz;
>>> end if;
>>>
>>> would be parsed in four ways, according to the four combinations of
>>> choices (enabled/disabled) for the two @ signs:
>>
>> [...]
>>
>> It is a trivial recursive-descent parser. "else" cannot follow "@",
>> because there is no statement starting with "else". Full stop.
>
> Of course, that would very much emasulate the feature (probably 25% of the
> @-code in Janus/Ada is to remove various "elsif" and "else" cases).
> [Remember, we designed this code to work on very small memory hosts, so
> anything not critical to the operation of the compiler is removed. One
> reason that I don't use that any more in production code.]
>
> Another common use that you wouldn't allow is to remove the exception
> handler from some code. (For Janus/Ada, the existence of an exception
> handler has a cost, so if it is not needed for production code, it is best
> completely eliminated.)
I think both cases would be happily handled by optimization:
if ... then
...
else
@ Something
end if;
Since @ Something becomes null, else null; is removed by the optimizer.
The same would happen with
exception
when ... =>
@ Something
[raise;]
> I think you could come up with a rule that would be less harmful to the
> feature than requiring full statements, especially for composite statements
> like if and case and blocks.
Maybe, but that would require more pages to explain in the RM (:-))
--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de
next prev parent reply other threads:[~2018-04-10 8:17 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-02 3:32 Interesting article on ARG work Randy Brukardt
2018-04-02 14:49 ` Dan'l Miller
2018-04-03 16:34 ` Bojan Bozovic
2018-04-03 22:33 ` Randy Brukardt
2018-04-04 2:12 ` Bojan Bozovic
2018-04-04 15:05 ` Dan'l Miller
2018-04-04 15:30 ` gerdien.de.kruyf
2018-04-04 16:09 ` Dan'l Miller
2018-04-04 22:30 ` Randy Brukardt
2018-04-04 22:43 ` Paul Rubin
2018-04-05 0:44 ` Mehdi Saada
2018-04-05 21:23 ` Randy Brukardt
2018-04-05 2:05 ` Bojan Bozovic
2018-04-05 22:12 ` Randy Brukardt
2018-04-06 13:35 ` Bojan Bozovic
2018-04-07 2:01 ` Randy Brukardt
2018-04-05 7:21 ` Dmitry A. Kazakov
2018-04-05 22:18 ` Randy Brukardt
2018-04-06 7:30 ` Dmitry A. Kazakov
2018-04-07 2:25 ` Randy Brukardt
2018-04-07 10:11 ` Dmitry A. Kazakov
2018-04-07 15:27 ` Dan'l Miller
2018-04-07 15:59 ` Dmitry A. Kazakov
2018-04-08 0:14 ` Dan'l Miller
2018-04-08 7:46 ` Dmitry A. Kazakov
2018-04-08 19:48 ` Dan'l Miller
2018-04-08 20:09 ` Dmitry A. Kazakov
2018-04-09 3:50 ` Dan'l Miller
2018-04-09 6:40 ` Jan de Kruyf
2018-04-09 7:43 ` Dmitry A. Kazakov
2018-04-09 13:40 ` Dan'l Miller
2018-04-09 14:13 ` Dmitry A. Kazakov
2018-04-09 14:36 ` Dan'l Miller
2018-04-09 14:44 ` Dmitry A. Kazakov
2018-04-09 15:03 ` Dan'l Miller
2018-04-09 16:12 ` Niklas Holsti
2018-04-09 16:30 ` Dmitry A. Kazakov
2018-04-09 16:45 ` Niklas Holsti
2018-04-09 17:33 ` Dan'l Miller
2018-04-09 19:47 ` Dmitry A. Kazakov
2018-04-09 20:24 ` Randy Brukardt
2018-04-10 8:17 ` Dmitry A. Kazakov [this message]
2018-04-09 18:08 ` Dan'l Miller
2018-04-09 21:17 ` Niklas Holsti
2018-04-09 22:09 ` Dan'l Miller
2018-04-10 19:23 ` Niklas Holsti
2018-04-10 19:46 ` Dan'l Miller
2018-04-15 7:50 ` Niklas Holsti
2018-04-15 13:31 ` Dan'l Miller
2018-04-15 18:37 ` Niklas Holsti
2018-04-09 20:14 ` Randy Brukardt
2018-04-06 23:49 ` Dan'l Miller
2018-04-12 10:21 ` Marius Amado-Alves
2018-04-15 13:07 ` Ada conditional compilation and program variants Niklas Holsti
2018-05-07 8:41 ` Jacob Sparre Andersen
2018-04-06 13:35 ` Interesting article on ARG work Marius Amado-Alves
2018-04-07 2:15 ` Randy Brukardt
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