From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Subject: Re: Gnat 2013 is out!
Date: Fri, 31 May 2013 14:03:08 +0200
Date: 2013-05-31T14:03:08+02:00 [thread overview]
Message-ID: <b0rhrsFkflsU1@mid.individual.net> (raw)
In-Reply-To: <alpine.DEB.2.02.1305311319150.13043@debian>
On 13-05-31 13:30 , Stefan.Lucks@uni-weimar.de wrote:
> On Thu, 30 May 2013, Randy Brukardt wrote:
>
>> "Adam Beneschan" <adam@irvine.com> wrote in message
>>
>>> I've always wanted some kind of feature in Ada that would allow a
>>> caller to provide a "dummy" for OUT parameters, without having to
>>> declare a new variable. The compiler would allocate a temporary
>>> object (and a separate one for each use of a "dummy") and then
>>> discard it after the call. It wouldn't work well when parameter
>>> types are unconstrained array or discriminant records, though.
>>
>> Hmm, that seems like a good idea to me.
To me too, but only of the "nice to have" priority.
>> But what would the syntax be? <>
>> maybe?
>>
>> My_Proc (Obj1, Obj2, Result => <>);
>>
>
> This has two issues:
>
> 1. This won't work if the type of Result is unconstrained, as, e.g., in
>
> procedure My_Proc(Obj1, Obj2: String; Result : String);
This is probably a very rare case.
>
> 2. This would sometimes break overload resolution -- which procedure
> should be called by "My_Proc (Obj1, Obj2, Result => <>);" if there
> happens to be another procedure in scope, such as
>
> procedure My_Proc(Obj1, Obj2: String; Result : Unbounded_String);
>
> I'd suggest
>
> My_Proc (Obj1, Obj2, Result => String(1 .. 80));
>
> or in general
>
> My_Proc (Obj1, Obj2, Result => type Name_of_Type);
It seems more consistent with the present language to allow type
qualification of the box, as in
My_Proc (Obj1, Obj2, Result => Name_of_Type'(<>));
> as syntactic sugar for
>
> declare
> Dummy : Name_Of_Type;
> begin
> My_Proc (Obj1, Obj2, Result => type Name_of_Type);
You probable meant this to be:
My_Proc (Obj1, Obj2, Result => Dummy);
> end;
If this proposal is taken up, I would like it to be extended with some
mechanism by which the called subprogram can query if a given out
parameter is actually a dummy <>, so that the subprogram can avoid
computing a useless value into that out parameter. However, that could
easily lead to distributed overhead.
--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
. @ .
next prev parent reply other threads:[~2013-05-31 12:03 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-29 13:36 Gnat 2013 is out! J-P. Rosen
2013-05-29 15:03 ` Simon Wright
2013-05-29 16:13 ` Simon Wright
2013-05-29 22:39 ` Randy Brukardt
2013-05-30 2:01 ` Adam Beneschan
2013-05-30 8:01 ` Bill Findlay
2013-05-30 23:09 ` Dennis Lee Bieber
2013-05-31 5:02 ` J-P. Rosen
2013-05-31 18:35 ` Bill Findlay
2013-05-30 10:39 ` Simon Wright
2013-05-30 16:21 ` Adam Beneschan
2013-05-30 19:53 ` Randy Brukardt
2013-05-31 7:41 ` Dmitry A. Kazakov
2013-05-31 11:30 ` Stefan.Lucks
2013-05-31 12:03 ` Niklas Holsti [this message]
2013-05-31 22:07 ` Randy Brukardt
2013-06-01 11:51 ` Georg Bauhaus
2013-06-03 14:52 ` Adam Beneschan
2013-06-04 17:42 ` Wesley Pan
2013-06-04 18:34 ` Adam Beneschan
2013-06-04 19:00 ` Wesley Pan
2013-06-05 15:40 ` Eryndlia Mavourneen
2013-06-11 2:39 ` Randy Brukardt
2013-06-11 6:31 ` Georg Bauhaus
2013-06-19 21:57 ` Randy Brukardt
2013-05-30 0:31 ` Dennis Lee Bieber
2013-05-31 16:12 ` dptrash
2013-06-01 5:10 ` Stephen Leake
2013-06-01 6:00 ` Per Sandberg
2013-06-01 6:46 ` J-P. Rosen
2013-06-01 15:22 ` Bill Findlay
2013-08-27 14:08 ` Yannick Duchêne (Hibou57)
2013-08-27 20:05 ` wilson
2013-08-27 22:59 ` Dennis Lee Bieber
2013-08-28 7:35 ` Dmitry A. Kazakov
2013-08-28 23:39 ` Dennis Lee Bieber
2013-06-07 2:41 ` gautier_niouzes
2013-06-07 15:52 ` mjsilva
2013-06-07 20:15 ` Dmitry A. Kazakov
2013-06-09 18:51 ` MatthiasR
2013-06-08 6:22 ` Simon Wright
2013-06-08 23:23 ` mjsilva
2013-06-10 11:07 ` Rego, P.
2013-06-13 13:30 ` Rego, P.
2013-06-17 6:35 ` Jacob Sparre Andersen
2013-06-22 8:17 ` MatthiasR
2014-03-18 0:04 ` Rego, P.
2013-06-11 7:52 ` Maciej Sobczak
2013-06-11 9:35 ` J-P. Rosen
2013-06-11 12:09 ` John Doe
2013-06-12 7:58 ` Maciej Sobczak
2013-06-12 11:01 ` G.B.
2013-06-12 20:01 ` Robert A Duff
2013-06-12 20:36 ` Georg Bauhaus
2013-06-13 7:38 ` Maciej Sobczak
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