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From: dewar@schonberg.cs.nyu.edu (Robert Dewar)
Subject: Re: Rules for Representation of Subtypes
Date: 1996/09/27
Message-ID: <dewar.843880362@schonberg>#1/1
X-Deja-AN: 185792672
references: <mheaney-ya023080002209961353500001@news.ni.net>
 <dewar.843570543@schonberg> <DyC5xn.K3L@thomsoft.com>
 <mheaney-ya023180002609962246250001@news.ni.net> <DyEqwA.My0@world.std.com>
organization: New York University
newsgroups: comp.lang.ada
Date: 1996-09-27T00:00:00+00:00
List-Id: <comp.lang.ada>


Bob said

"I'm not sure if I'm the Bob being addressed, but...   I think your
interpretation is correct.  However, in Ada 95, such a rule can't work.
Consider:

    type T is range 0..15;
    for T'Size use 4;
    subtype Bigger is T'Base range -15..15;

Clearly, Bigger'Size cannot be 4.
"



This is a baby and bathwater case!

Yes, of course the rule cannot apply to the unusual case of Bigger here, but
that is NOT a sufficient reason to throw out the entire rule, causing
incompatibilities.

In GNAT, we regard Bigger as a subtpye of the base type of T, not a subtype
of T for the purposes of the size ingheritance rules that apply to object
size (which is like the old Ada 83 size).