Help optimize D solution to phone encoding problem: extremely slow performace.

[Renato]

On Saturday, 20 January 2024 at 13:07:39 UTC, Renato wrote:
>
> D overhead with the fastest compiler, LDC, compared with Rust:
>
> ```
> 1.0
> 1.707627119
> 1.919527897
> 1.954595186
> 1.351342502
> 1.556217748
> ```
>

Oh sorry, I only posted the rates for the Linux benchmark...

On Mac M1, for some reason, D was a bit closer to Rust in some of 
the runs:

```
0.8611111111
1.819444444
2.018932874
2.0078125
1.069837447
1.165078285
```