Lua快速幂：对数级的乘方运算

-- 错误：逐次连乘，指数多大乘多少次
local result = 1
for _ = 1, exp do
    result = result * base
end

local function fastPow(base, exp)
    local result = 1
    while exp > 0 do
        if exp % 2 == 1 then
            result = result * base
        end
        base = base * base
        exp = math.floor(exp / 2)
    end
    return result
end
local label = panel:getChildByName("powText")
label:setString(tostring(fastPow(2, 20)))