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From: fraser@sinopsis.com (Fraser Wilson)
Subject: Re: A small Ada success story
Date: 1999/03/19
Message-ID: <921866918.613.55@news.remarQ.com>#1/1
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Organization: Vegetarian Ada Programmers
NNTP-Posting-Date: Fri, 19 Mar 1999 18:08:38 GMT
Newsgroups: comp.lang.ada
Originator: fraser@titanic
Date: 1999-03-19T00:00:00+00:00
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paene lacrimavi postquam bill@newsguy.com scribavit:

>Java does all that out of the box. I found Ada exception tracing to be weak
>compared to Java more powerfull exceptions. In Java, an exception is an object,
>that contains very usefull info that one can use.

I often wondered about an extension to the exception declaration syntax:

    Error : exception with record Exception_Type : Natural;  end record;

(Not that I'd ever use a Natural in this way of course!)

Mind you, Ada 95 gives you messages and stuff.

I think the problem with attaching a bunch of arbitrary information to an
exception is that the exception itself is supposed to be, well, exceptional.
Furthermore, if you read the Quality and Style guide, you'll notice that
it suggests providing query functions that can be used to prevent an
exception from being raised; e.g. for array-based stacks, a function
Stack_Is_Full.

Given all that, what would all this extra info buy you, apart from a
temptation to use exceptions as flow control?  In any case, you can always
query the package that raised the exception to find out what went wrong.

I fear I sound like one of the "Ada does it this way; therefore it must
be correct" zealots.  Oh, well.

Fraser.
(change i's to y's for my real email address)