I wanted to construct a CodepointSet from a string, so I used the
constructor here.
https://dlang.org/phobos/std_uni.html#.InversionList.this.2
I wrote a range of pairs (CodepointIntervals) of integers
consisting of each codepoint in the string paired with that plus
one. This did solve the problem, but only after I overcame some
peculiarities of the situation.
Specifically, this required a forward range, not just an input
range, so I wrote a save method.
Once I fixed that problem, it needed empty() and popFront() to be
pure. So I added the word pure to each in my range.
Once I fixed that problem, it required those to be @safe, so I
added that to my struct declaration of my range.
Then everything worked.
Could I have anticipated any of this, and what is the reason for
each of these?
