opNext: Simplified ranges

[Tomer at Weka]

On Sunday, 6 November 2022 at 01:48:04 UTC, Walter Bright wrote:
> We didn't use the "next" protocol for ranges because one cannot 
> test for existence of the next element without consuming it.

But that's exactly the issue - I have to produce the element in 
the range's ctor, which essentially requires a "non-popping 
popNext" to determine if it's empty and assign the front

-tomer