Clone of Lua's table library that uses '.n'
$ luarocks install --server=https://luarocks.org/dev table.n
Lua uses "sequences", i.e. tables with consecutive integer
keys and non-nil values, as arrays. But since one cannot
efficiently check whether a table is a sequence or not (and
in fact the default table library doesn't try), this leads
to some surprising bugs. Using an explicit `n` field to
denote table lengths is an alternative approach that's
(hopefully) easier to grasp and less error prone.