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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: S-expression I/O in Ada
Date: Tue, 10 Aug 2010 08:50:32 -0400
Organization: The World Public Access UNIX, Brookline, MA
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Date: 2010-08-10T08:50:32-04:00
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"Randy Brukardt" <randy@rrsoftware.com> writes:

> Not sure if it still exists in the real world, but the compiler we did for 
> the Unisys mainframes used Stream_Element'Size = 9.

Interesting.  Can these machines communicate with non-Unisys machines
over a regular TCP/IP network?  E.g. send an e-mail using standard
protocols, that can be read on a x86?

I assume Storage_Element'Size = 9, too.  Correct?

Next question: Is (was) there any Ada implementation where
Stream_Element'Size /= Storage_Element'Size?

>...(The Unisys mainframes 
> are 36-bit machines.) Stream_Element'Size = 8 would have made the code for 
> handling arrays awful.
>
> Similarly, Character'Size = 9 on that machine.

That sounds like a non-conformance, at least if the SP Annex
is supported.  Maybe you mean X'Size = 9, where X is of
type Character?  You'd certainly want 'Component_Size = 9
for array-of-Character.

> That would have made a compiler for the Unisys machines impossible; it would 
> have made streaming impossible. There is no sane way to put 36-bit values 
> into Octets - the only way that would have worked would have been to use 
> 16-bits for every 9-bit byte.
>
> Whether this is a significant consideration today (in 2010) is debatable, 
> but it surely was a real consideration back in 1993-4. So Ada 95 could not 
> have made this choice.

I think it would not be a good idea to make Ada unimplementable
on "odd-ball" machines.

- Bob