【高级技巧】函数缓存：重复计算的函数级缓存写法

local function memoize(fn)
    local store = {}
    local hits, total = 0, 0
    local function inner(...)
        local key = table.concat({...}, "|")
        local hit = store[key]
        total = total + 1
        if hit ~= nil then
            hits = hits + 1
            return hit, true
        end
        local value = fn(...)
        store[key] = value
        return value, false
    end
    local function stat()
        return hits, total
    end
    return inner, stat
end

local function rawScore(atk, def, hp)
    return atk * 0.5 + def * 0.3 + hp * 0.2
end
local scoreOf, scoreStat = memoize(rawScore)
local function onEquipChange(player)
    scoreOf, scoreStat = memoize(rawScore)
    sendmsg(player, 1, 0, "装备评分已刷新：" ..
        string.format("%.1f", scoreOf(getplayvar(player, "HUMAN", "Atk") or 0, 0, 0)))
end