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=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM
	autolearn=ham autolearn_force=no version=3.4.4
X-Google-Thread: 103376,9dec3ff1604723d9
X-Google-Attributes: gid103376,public
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news1.google.com!news2.google.com!proxad.net!newsfeed.stueberl.de!uucp.gnuu.de!newsfeed.arcor.de!news.arcor.de!not-for-mail
Newsgroups: comp.lang.ada
Subject: Re: Bitmanipulation in Ada
From: Bernd.Specht@gmx.com (Bernd Specht)
References: <Xns9549E5E9CFFB1BerndSpechgmxcom@151.189.20.10>
 <87k6vwrwym.fsf@insalien.org>
 <Xns9549EB926B2CBBerndSpechgmxcom@151.189.20.10> <opscx5geap5afhvo@localhost>
Organization: No company
Message-ID: <Xns954AC63A02C0DBerndSpechgmxcom@151.189.20.10>
User-Agent: Xnews/4.05.03
Date: 19 Aug 2004 17:30:17 GMT
NNTP-Posting-Date: 19 Aug 2004 19:30:17 MEST
NNTP-Posting-Host: cde0620f.newsread4.arcor-online.net
X-Trace: 
 DXC=SLFV]ZYi05IJ2=Pn8=T1[J:ejgIfPPldDjW\KbG]kaMHlSE5DYV?adAVoN=S]ccfiGWEh14DWb8DHhoe1_24QkCMc3j0kIhaR2I
X-Complaints-To: abuse@arcor.de
Xref: g2news1.google.com comp.lang.ada:2861
Date: 2004-08-19T19:30:17+02:00
List-Id: <comp.lang.ada>

"Ed Falis" <falis@verizon.net> wrote in news:opscx5geap5afhvo@localhost:

> On 18 Aug 2004 21:10:30 GMT, Bernd Specht <Bernd.Specht@gmx.com> wrote:
> 
>> OK, but this would result in an assignment operation (a memory move on
>> maschine code level). What I want is a real "overlay" (same storage  
>> location used for both), so reading the value would not need extra
>> instructions. 
> 
> In all implementations of which I'm aware (and I've been in the Ada  
> compiler business for over 20 years) no code would be generated for an  
> unchecked conversion where the source and target have the same size.

Sorry, but that's absolutely *nonsense*

Have a look at Ludovics code:

with Ada.Unchecked_Conversion;
procedure P is
   type Byte_Array is array (1 .. Integer'Size) of Boolean;
   pragma Pack (Byte_Array);
   for Byte_Array'Size use Integer'Size;
   function To_Byte_Array is new
      Ada.Unchecked_Conversion (Source => Integer, Target => Byte_Array);
   I : Integer := 42;
   B : Byte_Array := To_Byte_Array (I);
begin
   null;
end P;


You agree that "I" and "B" are located at different adresses? Do you 
*really* think that you need *no* code to move data from one address to 
another??? That's wrong! You need at least *one* instruction, and this can 
be time consuming - especially if the data is missaligned and/or the code 
runs in a multiprocessor environment.


> You sound like you're looking for things to complain about, by the way.

Sorry - but you seem to be a blatherer.


>  (and I've been in the Ada compiler business for over 20 years) 

Wow! Be happy.


> 
> - Ed

*plonk*