byuu says:

This WIP is just work on nall/primitives ...

Basically, I'm coming to the conclusion that it's just not practical to
try and make Natural/Integer implicitly castable to primitive signed and
unsigned integers. C++ just has too many edge cases there.

I also want to get away from the problem of C++ deciding that all math
operations return 32-bit values, unless one of the parameters is 64-bit,
in which case you get a 64-bit value. You know, so things like
array[-1] won't end up accessing the 4 billionth element of the array.
It's nice to be fancy and minimally size operations (eg 32-bit+32-bit =
33-bit), but it's just too unintuitive. I think all
Natural<X>+Natural<Y> expessions should result in a Natural<64> (eg
natural) type.

nall/primitives/operators.hpp has been removed, and new
Natural<>Natural / Integer<>Integer casts exist. My feeling is that
signed and unsigned types should not be implicitly convertible where
data loss can occur. In the future, I think an integer8*natural8 is
fine to return an integer64, and the bitwise operators are probably all
fine between the two types. I could probably add
(Integer,Natural)+Boolean conversions as well.

To simplify expressions, there are new user-defined literals for _b
(boolean), _n (natural), _i (integer), _r (real), _n# (eg _n8),
_i# (eg _i8), _r# (eg _r32), and _s (nall::string).

In the long-term, my intention is to make the conversion and cast
constructors explicit for primitive types, but obviously that'll shatter
most of higan, so for now that won't be the case.

Something I can do in the future is allow implicit conversion and
casting to (u)int64_t. That may be a nice balance.