In any case the use of Natural and Positive isn't really encouraged. They just
haven't specifically been removed or deprecated, because there isn't _that_
much of a reason to.
They're not really useful either because they only work for `int`. A proper
implementation would be like:
type
PositiveOrZero[T: SomeNumber] = range[T(0)..high(T)]
Positive[T: SomeInteger] = range[T(1)..high(T)]
proc foo(x: Positive[int]) = echo x
foo(1)
foo(-1) # error
Run
But this doesn't compile due to some weird range generics bug so we have to use
templates.
template positiveOrZero(T: type SomeNumber): untyped = range[T(0)..high(T)]
template positive(T: type SomeInteger): untyped = range[T(1)..high(T)]
proc foo(x: positive int) = echo x
foo(1)
foo(-1) # error
Run
