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From: Robert Dewar <robert_dewar@my-deja.com>
Subject: Re: Enumeration representation
Date: 1999/09/10
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Date: 1999-09-10T00:00:00+00:00
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In article <37d9061a@news1.prserv.net>,
  "Matthew Heaney" <matthew_heaney@acm.org> wrote:
> The image of literal B is of course "B".  But I don't know
what 'Img will
> return if you also use pragma Discard_Names.

Well, you know what we do to answer such questions, we consult
the super-secret archives known as the GNAT documentation,
carefully hidden from sight by being included in every
copy of GNAT distributed :-) There we find:

  <<Pragma Discard_Names causes names of enumeration literals to
    be suppressed. In the presence of this pragma, the Image
    attribute provides the image of the Pos of the literal, and
    Value accepts Pos values>>

The exact effect is implementation defined, and choosing the
pos seems as reasonable as any other choice. Choosing the
representation would be definitely a bad idea, the point of
a enumeration representation clause is that it does NOT affect
the semantics of programs, ONLY the representation.

> GNAT seems to be displaying the value of T'Pos.

which, considering the above documentation, is what we expect!

> You want to underlying representation.  If so, you'll have use
> Unchecked_Conversion to convert the literal to an integer, and
then display
> that.
>
> An alternative is to use the GNAT-specific attribute 'Enum_Rep
(I think
> that's what it's called).


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