Haskell 从枚举到实例？

这是一个纸牌数据结构 如何使

Card

可枚举，并从中使用

Enum

实例

Card{suit=Spade，pip=Ace}

，

Card{suit=Spade，pip=Two}

<代码>卡片{suit=Heart，pip=Ace}<代码>卡片{suit=Club，pip=Ace}<代码>卡片{suit=Diamond，pip=Ace}..Card{suit=Diamond，pip=King}

以下是我的做法（基本上是@epsilonhalbe的想法）：

这将为您提供：

data Suit
   = Spade | Heart | Club | Diamond
   deriving (Eq, Ord, Enum, Show, Bounded)

data Pip
   = Ace | Two | Three | Four | Five | Six | Seven | Eight | Nine
   | Ten | Jack | Queen | King
   deriving (Eq, Ord, Enum, Show, Bounded)

data Card = Card
     { suit :: Suit
     , pip :: Pip
     } deriving (Eq,Ord, Show, Bounded)

instance Enum Card where
  toEnum i =
    let (d,m) = i `divMod` (fromEnum (maxBound :: Pip) + 1)
    in Card (toEnum d) (toEnum m)
  fromEnum (Card s p) = fromEnum s * (fromEnum (maxBound :: Pip) + 1) + fromEnum p

---

---

PS：现在你应该得到全部-抱歉我弄乱了

maxBound

忘记了一个额外的提示使用

（fromEnum$maxBound Ace）*（fromEnum suit）+（fromEnum pip）

计算enumeration@epsilonhalbe你可能是指

（maxBound:：Pip）

或

King

对吧？（对于第一个你需要

派生（…，有界）

ya我总是弄错-我应该为此咨询文档，但是suit和pip在卡片中，如果suit和pip被maxBound分开怎么工作？maxBound应该是卡片{suit=Diamond，pip=King}@Joe看到了我的答案并开始玩它-基本上，这个想法是如何枚举图像中的像素-通过从上到下的行和从左到右的行中的像素（（0,0）->（1,0）->…（0,1）->（1,1）->…）-如果你想从（x，y）->索引开始，你可以计算y*图像宽度+x（然后用余数除法返回）-这里只有

x=Pip

和

y=Suit

data Suit
   = Spade | Heart | Club | Diamond
   deriving (Eq, Ord, Enum, Show, Bounded)

data Pip
   = Ace | Two | Three | Four | Five | Six | Seven | Eight | Nine
   | Ten | Jack | Queen | King
   deriving (Eq, Ord, Enum, Show, Bounded)

data Card = Card
     { suit :: Suit
     , pip :: Pip
     } deriving (Eq,Ord, Show, Bounded)

instance Enum Card where
  toEnum i =
    let (d,m) = i `divMod` (fromEnum (maxBound :: Pip) + 1)
    in Card (toEnum d) (toEnum m)
  fromEnum (Card s p) = fromEnum s * (fromEnum (maxBound :: Pip) + 1) + fromEnum p

λ> take 5 $ [minBound .. maxBound] :: [Card]
[Card {suit = Spade, pip = Ace},Card {suit = Spade, pip = Two},Card {suit = Spade, pip = Three},Card {suit = Spade, pip = Four},Card {suit = Spade, pip = Five}]