symmetric signed types

[Dominikus Dittes Scherkl]

On Thursday, 23 January 2014 at 20:35:56 UTC, Andrei Alexandrescu 
wrote:
>> byte a = -128;
>> auto b = -a;
>>
>> What type should b get? (of course "byte" but the value 
>> doesn't fit!)
>
> The type will be int.
Ah, ok. Of course the small types always become int.
But the problem would be the same with

long a = long.min;
auto b = -a;

does this return ulong (which could hold the correct result) or 
long (and a wrong result)?

>> integral types still suffer the same old flaws.
>
> There are quite a few improvements for integrals, too, most 
> importantly of the kind that don't exact a speed penalty.
I can understand that speed is critical for unsigned types but 
for me the main benefit of signed types is their "ease of use" - 
like in the "hello world" program it should be easy to do it 
right and work "out of the box". Errors like

int a = 2_000_000_000;
int b = a + a;

should not generate weird stuff like -294_967_296 (which it 
actually does) but better produce NaN to indicate that the result 
is not in the valid range or "int".
For addition that may be not to complicated to handle, but for 
multiplication? There it would be very nice (and fast!!) to have 
an implenetation that checks the carry and set the result to NaN 
if carry is not 0. At the moment doing so requires the use of 
inline assembler - not realy a newbi-thing to do...