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Date: 19 Sep 92 00:40:35 GMT
From: cis.ohio-state.edu!news.sei.cmu.edu!jbg@uunet.uu.net  (John Goodenough)
Subject: Re: Enumerations
Message-ID: <1992Sep19.004035.22312@sei.cmu.edu>
List-Id: <comp.lang.ada>

The one case in which you might expect a compiler to provide a default
enumeration representation different from that of the position number is for
the predefined type BOOLEAN.  My understanding is that on some architectures
it can be more efficient to code FALSE as a negative number (e.g., all ones)
and TRUE as a non-negative number (e.g., all zeroes).  As I recall, it was at
least partly for this reason that the LRM did not specify the default
representation for enumeration types.  

Robert Dewar is fond of pointing out (as a way of highlighting the common
confusion between an abstract value and its representation) that it should not
be considered peculiar that the LRM fails to specify a default representation
for enumeration values; it doesn't specify the default representation of
integers either!  

John B. Goodenough					Goodenough@sei.cmu.edu
Software Engineering Institute				412-268-6391