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From: Matthew Heaney <matthew_heaney@acm.org>
Subject: Re: Storage space question
Date: 1998/12/12
Message-ID: <m3iufhm64f.fsf@mheaney.ni.net>#1/1
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References: <366FE278.FAF73497@pwfl.com>
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NNTP-Posting-Date: Sat, 12 Dec 1998 12:55:38 PDT
Newsgroups: comp.lang.ada
Date: 1998-12-12T00:00:00+00:00
List-Id: <comp.lang.ada>

"David C. Hoos, Sr." <david.c.hoos.sr@ada95.com> writes:

> Matthew Heaney wrote in message ...
> >"As long as you only use the constants (not the literals), you get all
> >the type safety that an enumeration type buys you."
> >
> >The object will never get assigned the values 3 .. 7, because those
> >values aren't named by constants.
> >
> >If you stick to the constants, then there is no loss of type safety.
> >
> Well, what if the data structure was filled by, say, a read from a network.
> Use of the enumeration allows you to apply the 'valid test.

Yes, but you can validate input data by using a case statement, just
like we did in Ada83:

X : <unconstrained integer subtype>;

Read (fd, X);

case X is
   when Run | Stop | Turn =>
     <data OK>

   when others =>
     <handle bad data somehow>

end case;

Like representation clauses for enumeration types, the Valid attribute
just adds unnecessary complexity to the language.