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Subject: Re: Division by zero
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Date: Tue, 14 Jun 2005 20:21:26 +1200
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"Robert A Duff" <bobduff@shell01.TheWorld.com> wrote in message
news:wccfyvm78k0.fsf@shell01.TheWorld.com...

> Now I have a variable Gizmos, and I want to print out the
> numbers of Gizmos per Widget (when that's meaningful).
> In *portable* code, I might want to write:
>
>     if Widgets = 0 then
>         Put_Line("Unknown");
>     else
>         Put_Line(Image(Gizmos/Widgets));
>     end if;
>
> If divide by zero were illegal at compile time, even in unreachable
> code, the above would be annoying illegal on Unix.

Interesting example. I guess I'm taking it a bit on a tangent now
but how does that square off with RM 11.6.5 which says in part:

... The exception need be raised by the implementation only if, in the
absence of raising it, the value of this undefined result would have some
effect on the external interactions of the program ...

Yes, I know it's just an implementation permission and so doesn't define
the language. Yet, the idea seems to be that if there is no possible
observable
effect then it's ok. Shouldn't the same logic apply in your example as well?