Here’s one that I consider a bit odd—and I’m testing my own understanding
now. The following *is* a sequence, according to the definitions in Lua’s
manual: {10, 20, nil}. That’s a sequence, and it’s length is 2. It’s
a sequence because there is an n such that “the set of [the table’s]
positive numeric keys is equal to {1..n} for some non-negative integer n.”
And that n (here 2) is it’s length. (Someone please correct me if I’m
wrong.) Presumably this means that {[1] = 10, [2] = 20, [3] = nil} is also
a sequence, although with a more verbose constructor.