why $ is need to access array [negative index]?

[mipri]

On Friday, 18 September 2020 at 20:46:00 UTC, mw wrote:
> On Friday, 18 September 2020 at 20:06:01 UTC, Steven 
> Schveighoffer wrote:
>>
>> I would say no. The indexing code lowers to a machine 
>> instruction. Making it so a negative value means something 
>> else means every single indexing operation is going to have to 
>> check whether it's negative, and if so do something completely 
>> different.
>
> Currently we have range check on every single indexing 
> operation already; so the trade-off here is: adding one more 
> check v.s. the convenience it buys.

Range checks that never fire because your code isn't buggy
are very friendly to the branch predictor. Negative-indexing
checks are not so friendly.