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From: Kilgallen@SpamCop.net (Larry Kilgallen)
Newsgroups: comp.lang.ada
Subject: Re: calenday (was Re: IBM Acquires Rational Ada
Date: 20 Dec 2002 06:19:52 -0600
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In article <atv5fj$ldi$1@slb5.atl.mindspring.net>, "Marin David Condic" <mcondic.auntie.spam@acm.org> writes:

> I'd suspect that declaring in the standard that all tags shall start at
> offset 0 and extend for 32 bits would not cause anyone any rework. I doubt
> it would come up often that the offset needed to be anything other than
> zero - I can't think of why I'd want it to or why I couldn't make things
> work somehow if it were always zero. Having a predefined constant for size
> and a mandated (dare I use that word?) starting point at the beginning of
> the record ought to be good enough.

It depends on whether there are external constraints on the record.
VMS kernel data structures, for instance, use the first 64 bits for
a doubly-linked list, the next 16 bits for length and the 16 bits
after that for a "type" (the closest thing to a constraint or tag).

Interoperation with other languages is crucial in this domain, unlike
all-Ada environments.