F# 模式匹配嵌套可区分联合

Question

我有一个嵌套的歧视联合代表一副扑克牌:

type Symbol =
| Seven
| Eight
| Nine
| Ten
| Jack
| Queen
| King
| Ace

type Card =
| Heart of Symbol
| Diamond of Symbol
| Spade of Symbol
| Club of Symbol

现在我想写一个函数返回给定卡片的值，在我的例子中它与卡片花色无关:

let GetValue (card : Card) =
  match card with
  | Heart(Seven) -> 0
  | Diamond(Seven) -> 0
  | Spade(Seven) -> 0
  | Club(Seven) -> 0
  ...

这显然写起来很乏味。有没有办法做这样的事情

let GetValue (card : Card) =
  match card with
  | _(Seven) | _(Eight) | _(Nine) -> 0
  | _(Ten) -> 10
 ...

非常感谢。

Answer 1

您对数据的建模不正确。由于总套牌是西装和等级的完整笛卡尔乘积，因此将等级“包裹”在西装中是没有意义的。两者应该是独立的，同样重要的卡片属性:

type Rank =
  | Seven
  | Eight
  | Nine
  | Ten
  | Jack
  | Queen
  | King
  | Ace

type Suit =
  | Heart
  | Diamond
  | Spade
  | Club

type Card = { suit: Suit; rank: Rank }

let getValue (card:Card) = 
   match card.rank with
   | Seven | Eight | Nine -> 0
   | Ten -> 10
   ...