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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Exceptions
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Date: Mon, 10 Dec 2007 09:22:40 +0100
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Date: 2007-12-10T09:14:57+01:00
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On Sun, 09 Dec 2007 23:40:20 +0100, Georg Bauhaus wrote:

> Robert A Duff wrote:

>> I think there are some mistakes in the Java design for exceptions, but I
>> don't think the whole idea of exception contracts is bad.
>> 
> When Robert Dewar talked about exceptions at MIT (I think, that's
> from memory of a video recording), one of his arguments was that
> you don't want to write cascades of conditionals for handling
> return values (being either returned values or failure indicators)
> ---because that's a mess.
> 
> Now, when we have a sequence of statements in a block,
> 
>    P1(X); P2(X); ... ; Pn(X, Y);
> 
> then what will be the average number of exception handlers
> for this block? Involving how many different exceptions?

Close to 0.

1. How often do you declare a new exception when writing a new subprogram?
My guess is about 1 / 10_000.

2. How often does a caller "eat" an exception of the callee instead of
propagating it further? My guess is 1 / 10.

There is not that many handlers in a good designed code. This is probably
the reason why people forget to handle exceptions properly. They are not
that visible.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de