帮会训练场：成员练功的经验加成

local function trainExp(actor, guild)
    local inField = getsysvar("trainN_" .. guild) or 0
    local bonus = math.min(inField * 5, 50)
    local base = 100
    local exp = math.floor(base * (100 + bonus) / 100)
    setplayvar(actor, "trainExp",
        (getplayvar(actor, "trainExp") or 0) + exp)
    sendmsg(actor, 1, "经验 +" .. exp .. "（加成 "
        .. bonus .. "%，在场 " .. inField .. " 人）")
end

local function joinField(actor, guild)
    setsysvarex("trainN_" .. guild,
        (getsysvar("trainN_" .. guild) or 0) + 1)
end
local function leaveField(actor, guild)
    setsysvarex("trainN_" .. guild,
        math.max((getsysvar("trainN_" .. guild) or 1) - 1, 0))
end