programming-lua/exercises/ch05/ex5_8.lua

local function concat(strs)
    local res = ""
    for i = 1, #strs do
        res = res .. strs[i]
    end

    return res
end

local function random_str()
    return tostring(math.random(100000, 999999))
end

local strs = {}
for i = 1, 200000 do
    strs[i] = random_str()
end

local time_start = os.clock()
concat(strs)
local own_concat_time = os.clock() - time_start

print("Own concat time: " .. own_concat_time)

time_start = os.clock()
_ = table.concat(strs)
local table_concat_time = os.clock() - time_start

print("table.concat time: " .. table_concat_time)

print(("table.concat was %f%s faster"):format(own_concat_time / table_concat_time * 100, "%"))