[m-rev.] for review: add uint->uintN conversions

[Julien Fischer]

On Thu, 1 Jul 2021, Zoltan Somogyi wrote:

> 2021-07-01 00:07 GMT+10:00 "Julien Fischer" <jfischer at opturion.com>:
>> Aren't the bounds enforced by the call to char.base_digit_to_int/3?
>
> Yep, they are, my bad.

That said, I wonder if there would be much benefit in lifting the
test into base_string_to_int and adding unsafe_base_digit_to_int/3
(i.e. do the test once per string, rather than once per character)?

Julien.