Lua Memoize

function memoizify(memoizified, persistence)
    persistence = type(persistence) == "number" and persistence or 256
    local cache = {}
    return function(...)
        local inargs = {...}
        local outargs
        local useless = {}
        for key, value in pairs(cache) do
            local difference = false
            for ix = 1, #key do
                if key[ix] ~= inargs[ix] then
                    difference = true
                    break
                end
            end
            if difference then
                if persistence > 0 then
                    key[0] = key[0] - 1
                    if key[0] == 0 then useless[#useless + 1] = key end
                end
            else
                key[0] = persistence
                outargs = value
            end
        end
        for ix = 1, #useless do
            cache[useless[ix]] = nil
        end
        if not outargs then
            outargs = {memoizified(...)}
            inargs[0] = persistence
            cache[inargs] = outargs
        end
        return unpack(outargs)
    end
end