Title says it all. I want to know why Lua adds an n field to tables when using table.pack().
Literally this is how you can implement this:
function pack(...)
return { n = select("#", ...), ... }
end
-- pretty useless
I don't see a point as you can use {} to construct a table and #tbl to get how many elements there are in a table.
local tbl = table.pack('a', 'b', 'c', 'd')
print(tbl.n, #{ 'a', 'b', 'c', 'd' }) -- 4 4
-- Same thing
If you use next to traverse a table constructed with table.pack, it really ruins iteration. Ofc you can use ipairs but for those who don't? Oh and length operator won't count that n.
table.pack() need not return a sequence. It only does so iff all arguments are non-nil.
Thus, if you want to reverse it, you need the "n"-member in the general case.
table.unpack(t, 1, t.n)
And despite the implementation being pretty trivial, table.pack() is still a useful abstraction.