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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: Using the GNAT defined attribute: 'Enum_Rep
Date: 1997/09/06
Message-ID: <dewar.873592148@merv>#1/1
X-Deja-AN: 270371273
References: <97082719523509@psavax.pwfl.com>
 <340D6C5D.2E53@pseserv3.fw.hac.com>
Organization: New York University
Newsgroups: comp.lang.ada
Date: 1997-09-06T00:00:00+00:00
List-Id: <comp.lang.ada>


W.W.G. says

<<Is this true ?  Seems to me it's legal (though I've never seen
it happen) for an implementation to generate anything it wanted
for a representation as long as ordering, indexing, etc. worked.>>


No, not at all, the whole point of enumeration types is that this is the
one place where Ada *does* have something to say about representation.
The ACVC interpretation (and hence what all Ada compilers do), is that
if you use an enumeration representation clause, then the representation
must match that of integers of the same size.

And of course Pos and Val will NOT match representations assigned in
this manner. Wes, if we believed your claim above, we would be believing
that enumeration representation clauses have no runtime semantics. That
is not the case!