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Newsgroups: comp.lang.ada
Subject: Re: Structured exception information
References: <eog0g5$2bn$1@cernne03.cern.ch> <u7ivnp09z.fsf@stephe-leake.org>
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From: Stephen Leake <stephen_leake@stephe-leake.org>
Date: Sat, 20 Jan 2007 10:04:07 -0500
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Date: 2007-01-20T10:04:07-05:00
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:

> On Fri, 19 Jan 2007 04:47:28 -0500, Stephen Leake wrote:
>
>> Maciej Sobczak <no.spam@no.spam.com> writes:
>> 
>>> Doesn't feel as type-safe as advertised.
>> 
>> But you have not given an actual example where a string is not
>> a type-safe solution to the actual problem at hand.
>> 
>> The only example you have given is "present the error to the user". In
>> that case, a string is precisely the correct type.
>
> What about presenting an information necessary for handling the exception
> to the handler?

Ok, I would still like to see a precise example, not all this hand-waving.

> As a practical example, consider mail non-delivery. A returned mail plus
> traceback is the information to you, the handler from the exception point.

To me, bounced emails are _not_ "exceptional" events in mail handling
systems; they are expected, even "normal". As for the failed
temperature sensor in another thread, out-of-band status information
is a cleaner way to handle this.

Can you show some example Ada code for this? And explain why
exceptions are better than status for this case?

-- 
-- Stephe