pub const PAIRS: usize = 3;Expand description
How many disjoint intervals a range holds before it collapses to their hull.
Three, which section 10.2 says covers x != 0, x != 0 && x != 1, and the exclusions a
switch produces. A fourth interval is not free: every operation over ranges is quadratic in
this number, so the arithmetic that comes next pays for it nine times over.