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Date: Sun, 15 May 2011 07:35:30 -0700
From: Patricia Shanahan <pats@acm.org>
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Subject: Re: Java puzzler
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On 5/15/2011 3:16 AM, Tom Anderson wrote:
...
> Fair enough. I suppose my position is that this hardware ability has to
> be used in the service of some solidly well-defined software semantics.
> Throwing exceptions at random from arithmetic expressions is not what i
> think of as solidly well-defined.
...

I agree. Throwing an exception if *any* expression evaluation results in
a value that is not representable in the type of the expression would
not be "at random". It would be well-defined through the existing
specification of how to evaluate arithmetic expressions.

Making the throw dependent on whether and how the expression had been
optimized would make it unpredictable, and varying from compiler version
to compiler version, a very bad thing.

I don't think adding exceptions for arithmetic overflow would be a
sensible change as a modification for Java. If it affected existing code
it would break a lot of programs. If it did not, it would add a lot of
complexity to the language. It is something that might be useful in a
language designed for it.

Patricia