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Date: Sun, 15 May 2011 07:37:37 -0700
From: Patricia Shanahan <pats@acm.org>
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Subject: Re: Java puzzler
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On 5/15/2011 5:40 AM, markspace wrote:
> 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 guess I'm not understanding what people think is wrong with the
> semantics of "overflow." Overflow is very well defined. It's something
> like 8 gates on the hardware level, and happens at the same speed as the
> the add or subtract itself. I.e., about 1 CPU cycle in most cases nowadays.
>
> By contrast, the current semantics of integer math are that sometimes
> you get the right answer and sometimes you don't. I consider that to be
> non-deterministic.

It is totally deterministic. It is just arithmetic modulo 2**32 for int,
2**64 for long etc.

Patricia