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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Subject: Re: In case statment? (was Re: is exception when others => null;
 smart?)
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Date: Fri, 25 Oct 2002 14:59:41 GMT
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Preben Randhol <randhol+news@pvv.org> writes:

> Now my next question is should a case statment be:
> 
>    case Number is
> 
>       when others =>
>          null;
>    end case;
> 
> Or simply:
> 
>    case Number is
> 
>    end case;
> 
> I'm leaning towards the latter as this is also how ada-mode does it.

"When others" is usually a very bad idea, and editors should not
encourage it.  One of the great benefits of Ada is the full-coverage
checking you get (at compile time!) on case statements and aggregates.
(Compared to other languages which default to "when others => null;" or
use run-time checking.)

Some folks think "when others" is just a shorthand for all the rest of
the enumeration literals (or whatever) in the type, that you don't feel
like typing in.  After all, that's what the RM says.  But I think "when
others" really means "all the others, INCLUDING the ones that will be
invented next week or next year".  So you should use "when others" only
when you're pretty sure all the others that will ever be invented must
necessarily fall into the same category.  That's rare.

So I agree: choose the latter.

- Bob