core.checkedint

[Andrei Alexandrescu via Digitalmars-d]

On 06/24/2016 08:11 PM, Walter Bright wrote:
> On 6/24/2016 4:59 PM, Andrei Alexandrescu wrote:
>> On 06/24/2016 07:56 PM, Walter Bright wrote:
>>> I believe adding such behavior is beyond the charter of checkedint.
>>
>> Which checkedint? The one in core? -- Andrei
>
> Your Checked!int. Sorry for the confusion.

Though you should be able to implement that via a hook, I think at this 
point we need to agree to disagree. The relevant code is at 
https://gist.github.com/andralex/a0c0ad32704e6ba66e458ac48add4a99#file-checked-d-L88:

     static if (!isUnsigned!L)
     {
         if (lhs < 0)
         {
             return subu(Result(rhs), Result(negs(lhs, overflow)),
                 overflow);
         }
     }

With your suggestion, this would also be an overflow:

long x = -1;
auto y = array.length + x;

I would be hard pressed to acknowledge that as an overflow that needs to 
be dynamically signaled. And the beauty of two's complement is that 
indeed it just works.


Andrei