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From: "David C. Hoos, Sr." <david.c.hoos.sr@ada95.com>
Newsgroups: comp.lang.ada
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 <FOPl6.864$Vz2.141381754@newssvr16.news.prodigy.com>
Subject: Re: Representation clause
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NNTP-Posting-Date: Sun, 25 Feb 2001 12:22:58 PST
Date: Sun, 25 Feb 2001 14:22:48 -0600
Xref: supernews.google.com comp.lang.ada:5523
Date: 2001-02-25T14:22:48-06:00
List-Id: <comp.lang.ada>

The fact that a given compiler may do reasonable things when the
sizes of the actual parameters of an instantiation of
Ada.Unchecked_Conversion are unequal, is not a property on
which I would like to depend.  However, since there is at least one
compiler for which my comment is not true, I have modified my
comment to read as follows:

   -- The enumeration's 'Size attribute must be the same as that of
   -- the representation type, else the effect is implementation-
   -- defined; in particular, the result can be abnormal (see
   -- RM95 13.9.1).

Now, of course, in the case of discontiguous representation, (the
case for the example code) the result can still be abnormal for the
Value function.  Accordingly, the package client may either test
the result with the 'Valid attribute, or opt to have an exception
raised.

"Ken Garlington" <Ken.Garlington@computer.org> wrote in message
news:FOPl6.864$Vz2.141381754@newssvr16.news.prodigy.com...
> "David C. Hoos, Sr." <david.c.hoos.sr@ada95.com> wrote in message
> news:fEOl6.129219$Ch.23956265@newsrump.sjc.telocity.net...
>
> :    -- The enumeration's 'Size attribute must be the same as that of
> :    -- the representation type, else a compile error will occur when
> :    -- instantiating the generic package.
> :    for Colors'Size use Integer'Size;
>
> By the way: on GNAT 3.13p, the following will generate a compiler
_warning_,
> but will compile:
>
>    for Colors'Size use 3;
>
> The  test program also ran successfully.
>
> You may wish to modify the comments appropriately.
>
>