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From: dewarr@my-dejanews.com
Subject: Re: Y2K Issues
Date: 1998/10/31
Message-ID: <71dott$cm0$1@nnrp1.dejanews.com>#1/1
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 <F1Lt90.HEx.0.-s@inmet.camb.inmet.com> <71ckkt$n4a$1@nnrp1.dejanews.com>
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Date: 1998-10-31T00:00:00+00:00
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In article <71ckkt$n4a$1@nnrp1.dejanews.com>,
  dennison@telepath.com wrote:
> In article <F1Lt90.HEx.0.-s@inmet.camb.inmet.com>,
>   stt@houdini.camb.inmet.com (Tucker Taft) wrote:
>
> > (FWIW, from my point of view, the fact that the code for such
> > grand-children is likely to be implementation-specific doesn't seem like
> > enough of a reason to disallow them, since the whole point may be to
provide
> > a stable interface to some additional functionality via a
> > grand-child, recognizing that the implementation of the functionality may
> > need to be revised when porting to a new compiler or new release.  Clearly
> > the "caveat emptor" is critical here.)
>
> It sure would have helped me a lot a few days ago if I could have made my
> package Ada.Real_Time.Float_Conversions, instead of
> Real_Time_Float_Conversions. Apparently Green Hills decided to disallow
> children of their pacakges. My implementation of this package is *still*
> dependent on their implementation of Ada.Real_Time.Time_Span. Its just that I
> was forced to do Unchecked_Conversions to accomplish it. (I feel so dirty!)
> And now when their implementation does change, I might not notice until
> runtime. If they'd let me make a child package I could have gotten a compile
> error when the implemetation changes.


You cannot count on having got a compile error if the implementation changes.
You might or might not. Just as your unchecked conversion might have got a
warning if the sizes were different (I assume your compiler provides this
important warning).

If using unchecked_conversion makes you feel dirty, then compiling
grandchildren of Ada that depend on private data structures should make
you equally queasy, if not more so!

Robert Dewar

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