Re: Structured exception information

["Randy Brukardt" <randy@rrsoftware.com>]

"Robert A Duff" <bobduff@shell01.TheWorld.com> wrote in message
news:wcc64b7or96.fsf@shell01.TheWorld.com...
> "Randy Brukardt" <randy@rrsoftware.com> writes:
>
> > We did look at this issue when working on the Amendment. The "obvious"
> > answers seem to have issues with visibility and compatibility with
existing
> > Ada.Exceptions mechanisms.
>
> If we had done it right in Ada 95, we wouldn't have had the
> Ada.Exceptions kludge in the first place, so no need to be complatible
> with it.

Well, don't look at me on that one... ;-)

> I don't know what the visibility issues were, so I can't comment on
> that.  Do you happen to know which AI this was?

Not off-hand, but it only takes a minute to look up...

It was AI-264, "Exceptions as types". The title alone suggests trouble: the
main issue is to provide type-safe data along with exceptions. The minor
issue is a better way to deal with sets of exceptions. Neither of those
necessarily require making exceptions into types.

My personal feeling is that we solved a lot of the problems that we had with
the exception proposal when we dealt with all of the issues that nested
tagged types brought up. When we considered AI-264, we hadn't yet gone
through that exercise, and the entire thing looked impossible. Having solved
some of the related issues, it would be easier to deal with now. It would be
even easier if we had a mechanism for user-defined 'Image (which would allow
automatic converting to strings to keep the existing Ada.Exceptions routines
working).

                                      Randy.