From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.1 required=5.0 tests=BAYES_00,
	PP_MIME_FAKE_ASCII_TEXT autolearn=no autolearn_force=no version=3.4.4
Path: 
 buffer1.nntp.dca1.giganews.com!border1.nntp.dca1.giganews.com!nntp.giganews.com!usenet.blueworldhosting.com!feeder01.blueworldhosting.com!feeder.erje.net!1.eu.feeder.erje.net!gandalf.srv.welterde.de!news.jacob-sparre.dk!loke.jacob-sparre.dk!pnx.dk!.POSTED!not-for-mail
From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Ada design bug or GNAT bug?
Date: Sat, 4 Jul 2015 19:48:35 -0500
Organization: Jacob Sparre Andersen Research & Innovation
Message-ID: <mn9ut3$v54$1@loke.gir.dk>
References: <yo94phsbcvht$.1bktwe2qoqntt$.dlg@40tude.net>
	<mm58b5$9k0$1@loke.gir.dk>
 <4lrj5zz2u2z.u8x9cf7xzic6.dlg@40tude.net>	<mm9h84$5n8$1@loke.gir.dk>
	<d4629c07-4005-4bd3-8fa6-85d088fb83c9@googlegroups.com>
	<58f64fa9-7d0b-44dd-870c-77d9afcb82c4@googlegroups.com>
	<mn4jj1$n50$3@loke.gir.dk>
	<4228c0ea-837d-42a0-b2a8-a98d8d30f820@googlegroups.com>
 <lyy4iwxt4m.fsf@pushface.org> <mn8hok$fdf$1@dont-email.me>
NNTP-Posting-Host: rrsoftware.com
X-Trace: loke.gir.dk 1436057316 31908 24.196.82.226 (5 Jul 2015 00:48:36 GMT)
X-Complaints-To: news@jacob-sparre.dk
NNTP-Posting-Date: Sun, 5 Jul 2015 00:48:36 +0000 (UTC)
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 6.00.2900.5931
X-RFC2646: Format=Flowed; Original
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157
Xref: number.nntp.giganews.com comp.lang.ada:193923
Date: 2015-07-04T19:48:35-05:00
List-Id: <comp.lang.ada>

"Björn Lundin" <b.f.lundin@gmail.com> wrote in message 
news:mn8hok$fdf$1@dont-email.me...
> On 2015-07-04 09:46, Simon Wright wrote:
>> Shark8 <onewingedshark@gmail.com> writes:
>>
>>> Also, I seem to recall your dislike of INTERFACEs -- in hindsight,
>>> what would you have done differently if you needed the mechanism of
>>> "Type T has functions X, Y, and X" applied to a group of types?
>>> Generics, or some variations thereof?
>>
>> Generic signature packages?
>>
>
> I had this problem when implementing another companies proprietary
> communications protocol, that we needed to communicate with.
> The physical devices were picking-robots.
> All messages had a common headers and then message specific fields.
> And they had to have certain functions. To_String, Save_to_Database,
> Send, etc.
>
> Since I had complete control over the implementation, I
> ended up using inheritance from an abstract type.
>
> Some functions of the abstract type were implemented,
> and others - to specialized for the inherited type -
> was declared abstract.

Right, with single inheritance. Good enough for 98% of problems, IMHO. I've 
used abstract types this way (in Claw and in Claw tools), but I found that 
the main gain was the shared implementations that could be provided by the 
abstract type. Interfaces don't allow them, so they provide cool-looking, 
but mainly useless capabilities.

                                 Randy.