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=-0.3 required=5.0 tests=BAYES_00,
	REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,38fc011071df5a27
X-Google-Attributes: gid103376,public
X-Google-ArrivalTime: 2003-05-31 10:16:17 PST
Path: 
 archiver1.google.com!news1.google.com!newsfeed.stanford.edu!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!newsfeed.icl.net!newsfeed.fjserv.net!news-FFM2.ecrc.net!newsfeed.vmunix.org!fu-berlin.de!uni-berlin.de!dialin-145-254-039-076.arcor-ip.NET!not-for-mail
From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Ideas for Ada 200X
Date: Sat, 31 May 2003 19:18:41 +0200
Organization: At home
Message-ID: <bbao0u$7icu0$1@ID-77047.news.dfncis.de>
References: <6a90b886.0305262344.1d558079@posting.google.com>
 <VjOAa.16051$8g5.257873@news2.e.nsc.no> <3ED41344.7090105@spam.com>
 <3ED46D81.FF62C34F@0.0> <3ED46E07.4340CABC@0.0>
 <3ED4F3FD.A0EF7079@alfred-hilscher.de> <xIeBa.1017346$3D1.597085@sccrnsc01>
 <bebbba07.0305292326.75f5fbef@posting.google.com> <u4r3co12f.fsf@nasa.gov>
 <bebbba07.0305301649.45b78d8c@posting.google.com> <uvfvrobrb.fsf@wanadoo.fr>
 <bb9vp8$7bkb8$3@ID-77047.news.dfncis.de> <uisrrnxzk.fsf@wanadoo.fr>
 <BAFE6FC5.2ECD%yaldnifw@blueyonder.co.uk>
Reply-To: mailbox@dmitry-kazakov.de
NNTP-Posting-Host: dialin-145-254-039-076.arcor-ip.net (145.254.39.76)
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7Bit
X-Trace: fu-berlin.de 1054401376 7943104 145.254.39.76 (16 [77047])
User-Agent: KNode/0.7.1
Xref: archiver1.google.com comp.lang.ada:38226
Date: 2003-05-31T19:18:41+02:00
List-Id: <comp.lang.ada>

Bill Findlay wrote:

> On 31/5/03 12:42, in article uisrrnxzk.fsf@wanadoo.fr, "Pascal Obry"
> <p.obry@wanadoo.fr> wrote:
>> 
>> Right! I must be a bit tired to forget that :) So I think it could be
>> /:= *:= +:= and -:= (operators before the :=).
> 
> What about and, or, xor, rem and mod? "mod:=" ? I hope not!

You forgot :**= and unary :+=, :-=, :not=. For example:

X :not=; -- C people will envious! (:-))

> I find this proliferation of special notations revolting.

Rather tasteless, I would better allow:

   procedure "+" (L in out T; R : T);

then one could write:

declare
   X : T := ...;
begin
   X + 1;

> An "idem" feature, meaning, "the same as the destination" and used thus:
> 
> 1.  I := (idem + 1);  -- or perhaps: (<> + 1); or maybe: (all + 1);
>
> 2.  I := (1 - idem);  -- N.B. not possible using any ?:= operator
> 
> 3.  X := 0.5*(idem + a/idem);

And crowning:

4.  I : Integer := idem + 1;  -- OK, just a joke

> gives a lot more expressive power than update-in-place operations, but
> allows the latter to be implemented very easily in most cases that
> significant efficiency gains are possible (though not, admittedly,
> arithmetic operations overloaded on matrices and other structures for
> which conventional, if slightly heavier, procedural notations remain).

I have an alternative / additional proposal. The programmer declares 
in-place operations and instructs the compiler to deduce unary and infix 
operators from them. 

For example:

procedure Inc (X : in out T; By : T);
function "+" (X, Y : T) return T;
for "+" use Inc (X => X, By => Y);

> The idem notation also documents the programmer's intention more clearly
> in the cases (such as 3) in which the RHS subexpression is necessarily the
> same as the LHS, but which do not fit the limitations of a ?:= operation.

-- 
Regards,
Dmitry A. Kazakov
www.dmitry-kazakov.de