abs and minimum values

Siarhei Siamashka siarhei.siamashka at gmail.com
Sun Oct 31 07:22:57 UTC 2021

On Thursday, 28 October 2021 at 21:23:15 UTC, kyle wrote:
> ```
> void main()
> {
>     import std.math : abs, sgn;
>     alias n_type = short; //or int, long, byte, whatever
>     assert(n_type.min == abs(n_type.min));
>     assert(sgn(abs(n_type.min)) == -1);
> }
> ```
> I stumbled into this fun today. I understand why abs yields a 
> negative value here with overflow and no promotion. I just want 
> to know if it should. Should abs ever return a negative number? 
> Thanks.

I think that the best way to deal with this stuff without losing 
sanity is to introduce a special constant "n_type.nan" for signed 
integer data types. Then you get "abs(n_type.nan) == n_type.nan", 
which makes more sense.

All the uses of "n_type.min" in your code can be replaced either 
with "n_type.nan" or "-n_type.max", depending on the context and 
your intention. The existing constant "n_type.min" can be 
deprecated for signed integer types. Compilers and static 
analysis tools could warn about its use.

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