【高级技巧】策略模式：伤害公式的可插拔封装

local STRATEGIES = {
    subtract = function(atk, def)
        return math.max(atk - def, atk * 0.1)
    end,
    multiply = function(atk, def)
        return math.floor(atk * (1 - math.min(def / (def + 1000), 0.8)))
    end
}

local current = "multiply"
local function setStrategy(name)
    if STRATEGIES[name] then
        current = name
    end
end
local function calcDamage(atk, def)
    return STRATEGIES[current](atk, def)
end
print(calcDamage(1000, 500))
setStrategy("subtract")
print(calcDamage(1000, 500))