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From: Maciej Sobczak <no.spam@no.spam.com>
Newsgroups: comp.lang.ada
Subject: Re: Structured exception information
Date: Tue, 16 Jan 2007 11:45:54 +0100
Organization: CERN News
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Date: 2007-01-16T11:45:54+01:00
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Dmitry A. Kazakov wrote:

> I think that a more "obvious" answer to me would be a contracted model of
> exceptions a-la Java. Then we would have in Georg's case (the syntax is
> imaginary):
> 
>    procedure Foo raises Foo_Error; -- Compile error!
> 
>    procedure Foo is
>       type Foo_Error is exception with ...;
>    begin
>       ...
>       raise Foo_Error'(...);
>       ...

or maybe:

         raise Foo_Error with (A => X; B => Y; C => Z);

as a natural extension for raise with message.

> One problem with above is that 
> 
>    procedure Foo raises Some_Error'Class;
> 
> should be illegal.

Why? You would need to allow it at least in those subprograms that 
accept class-wide parameters, otherwise the open-close principle of OO 
would not hold (it would not be possible to extend the given hierarchy 
without messing with *all* the subprograms that operate on existing 
class-wide types).


-- 
Maciej Sobczak : http://www.msobczak.com/
Programming    : http://www.msobczak.com/prog/