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From: Matthew Heaney <matthew_heaney@acm.org>
Subject: Re: Storage space question
Date: 1998/12/12
Message-ID: <m3pv9pnc5m.fsf@mheaney.ni.net>#1/1
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References: <366FE278.FAF73497@pwfl.com>
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NNTP-Posting-Date: Fri, 11 Dec 1998 21:47:44 PDT
Newsgroups: comp.lang.ada
Date: 1998-12-12T00:00:00+00:00
List-Id: <comp.lang.ada>

Marin David Condic <condicma@bogon.pwfl.com> writes:

> > As long as you only use the constants (not the literals), you get all
> > the type safety that an enumeration type buys you.
> > 
> > Which is why rep clauses for enumeration types is overkill, that adds
> > unnecessary complexity to the language.
> 
> Well, not quite all the type safety. Suppose that the field occupies 3
> bits but only the values 0, 1 and 2 are currently valid. Or worse, only
> the values 2#001#, 2#010# and 2#100# are valid. With an integer type,
> there is no way of eliminating the invalid values. With enumerations,
> you can't accidentally get an invalid bit pattern assigned to the
> register field.

"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.