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From: "Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>
Newsgroups: comp.lang.ada
Subject: Re: Ada package registry?
Date: Fri, 5 Feb 2016 23:09:25 -0700
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Date: 2016-02-05T23:09:25-07:00
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On 02/05/2016 06:25 PM, Randy Brukardt wrote:
> 
> [What I mean by expressing assumptions is that it's unlikely that any real 
> Ada code would really run anywhere. I've been having fun with Gautier over 
> his "unconditional portability" claim, as one only needs a single 
> counter-example to disprove the claim. After a few obvious problems with the 
> choices of Janus/Ada were worked out, I pointed out that his types wouldn't 
> work on our old U2200 compiler (as that was a 1's completement, 36-bit 
> machine). He decided quite reasonably not to worry about that, but that 
> means in his case, that means his code is "unconditionally portable" so long 
> as your target supports 32-bit integers and is 2's complement. That might be 
> 99% of machines, but its not quite unconditional.]

Wasn't that an Ada-83 compiler? And isn't he trying for portability across
Ada-95 compilers?

If you had an Ada-95 compiler for that machine, what would be the problem with

type U is mod 2 ** 32;
for U'Size use 32;

type S is range -(2 ** 31) .. (2 ** 31) - 1;
for S'Size use 32;
?

(I guess in Ada 83 you could do

type U is range 0 .. (2 ** 32) - 1;
for U'Size use 32;

There'd be plenty of room in the base type for the corresponding negative
values, unlike a 32-bit machine.)

-- 
Jeff Carter
"We burst our pimples at you."
Monty Python & the Holy Grail
16