【进阶实战】Lua NaN陷阱：裁决之杖伤害系数算出永假的0/0

local function crit(actor, def)
    local k = 500 / (def - def)        -- 0/0 得 NaN
    if k > 1 then                      -- NaN比较恒false，静默
        giveitem(actor, "裁决之杖", 1, 0, "暴击馈赠")
    end
end

local function crit(actor, def)
    local k = 500 / math.max(def - def, 1)   -- 分母钳制，禁0
    if k ~= k then return end                -- NaN哨兵拦截
    if k > 1 then
        giveitem(actor, "裁决之杖", 1, 0, "暴击馈赠")
    end
end