据说我希望ThenByDescending使用Reservation。有许多类型的deposit，例如为普通客人预订，或贵宾，......（例如VIP可以在存入大量金钱时获得更高的折扣等）。
Reservation如果我有很多记录，那么应用程序是否会占用大量内存？
至于上面的例子，我创建了一个私有的可变变量来存储钱，这很糟糕。如何在不将namespace RoomBooking
type ReservationType =
| Normal
| VIP
| Custom
...
type Reservation =
{ ``type`` : ReservationType
incrDeposit : decimal -> unit
decrDeposit : decimal -> unit }
module Reservation =
let init deposit = function
| Normal | Custom as t ->
let mutable deposit = if deposit > 0m then deposit else 0m
{ ``type`` = t
incrDeposit = fun d -> if d > 0m then deposit <- deposit + d
decrDeposit = fun d -> if deposit > d then deposit <- deposit + d }
| VIP ->
...
let customInit incrDeposit decrDeposit =
{ ``type`` = Custom
incrDeposit = incrDeposit
decrDeposit = decrDeposit }
暴露给外部的情况下使功能正常工作？