ow Integers Should Work

Don nospam at nospam.com
Mon Dec 5 13:37:24 PST 2011

On 05.12.2011 18:36, bearophile wrote:
> Manu:
>> Also, contrary to his claim, I find that wrapping is usually what I
>> DO want in this case..
>> It's super rare that I write any code that pushes the limits of an int
>> (unless we're talking 8-16 bit, see my range+saturation comment before),
>> and when I do write code that pushes the range of an int, I can't think of
>> a time when I've not wanted to wrap as expected.
> The code you usually write seems rather unusual. I have kind of the opposite situations.
> But first of all, "trapping" ints are needed to avoid bugs in normal code. Some bugs are shown here:
> http://embed.cs.utah.edu/ioc/

Those mostly aren't relevant for D. C has many cases of undefined 
behaviour because it doesn't require twos-complement arithmetic. D 
doesn't have that problem.
We still need to tidy up the semantics of << and >> to remove undefined 
behaviour. But it's hard to do much more than that.

The "overflow12.pdf" paper on that site shows statistics that overflow 
is very often intentional. It's strong evidence that you *cannot* make 
signed overflow an error. Even if you could do it with zero complexity 
and zero performance impact, it would be wrong.

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