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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: Quality systems (Was: Using Ada for device drivers? (Was: the
   Ada mandate, and why it collapsed and died))
Date: 23 May 2003 17:21:38 -0400
Organization: The World Public Access UNIX, Brookline, MA
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Date: 2003-05-23T17:21:38-04:00
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:

> Randy Brukardt wrote:
> 
> > Virtually every time I use a modular type, I end up tracking down some
> > bug at runtime that would have been caught had there been an overflow
> > check. (Typically in the creation of an array index or the like.) Most
> > of the these types are 'indexes' (handles) that have to fit in a
> > particular size, and I often write checks like:
> >     if Index-1 > 0 then
> >         Index := Index - 1;
> >     end if;
> > which is wrong for a modular type. (Consider Index=0).
> 
> But a modular type should have no "<" defined! A transitive "<" is 
> incompatible with modular "+" and "-".

But I think Randy and I are saying that a type with transitive "<"
should not have modular semantics.

- Bob