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From: "Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>
Newsgroups: comp.lang.ada
Subject: Re: AI12-0218: What is the portable representation clause for
 processing IETF packets on little-endian machines?
Date: Fri, 11 May 2018 23:56:15 +0200
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Xref: reader02.eternal-september.org comp.lang.ada:52297
Date: 2018-05-11T23:56:15+02:00
List-Id: <comp.lang.ada>

On 05/11/2018 11:39 PM, Simon Wright wrote:
> 
> whereas Ada2012 says
> 
>      "To convert a record from one representation to another, two record
>      types with a common ancestor type need to be declared, with no
>      inherited subprograms."
> 
> which seems to require _three_ types.

The example in 13.6 shows this with only 2 types. This is because a type is 
defined to be its own ancestor (ARM 3.4.1).

> But in any case your code doesn't answer my question: what
> representation trick could convert between
> 
>     type T is record
>        J : Integer;
>     end T;
> 
> and
> 
>     type BE_T is new T;
>     for BE_T use record
>         ?????
>     end record;

I was showing how to use records with representations to get the compiler to do 
byte swapping for you. There's no way to use them to change the byte order of an 
integer type directly.

-- 
Jeff Carter
"Since I strongly believe that overpopulation is by
far the greatest problem in the world, this [Soylent
Green] would be my only message movie."
Charleton Heston
123