Re: Possible bug with the length operator

[Mason Larobina <mason.larobina@...>]

I have a current usecase in public code which uses a grey area (as far
as I can see) in the current len operator definition.

My code creates holes to truncate items from a list but the len
operator is never called while the table has holes in it.

This is a cut down example of the method:

#!/usr/bin/env lua
-- Items are created or cleared to meet the required new_size
function update(t, new_size)
    local tlen = #t -- cache item size
    for i=1, math.max(tlen, new_size) do
        if i > new_size then
            t[i] = nil -- collect item
        else
            if not t[i] then
                t[i] = true -- create item
            end
            -- do something
        end
    end
end
local t = {}
for _, new_size in ipairs{10, 1, 100, 60, 30, 65, 8, 64} do
    update(t, new_size)
    assert(#t == new_size, "size mismatch")
    print(#t, new_size)
end

I've never seen an incorrect size returned by #t so far but is this
behaviour subject to change in later lua versions?

Mason