推導查看代數數據類型

Question

我有以下幾種類型：

data Suit = Club | Diamond | Heart | Spade deriving Show 
data Rank = R2 | R3 | R4 | R5 | R6 | R7 | R8 | R9 | R10 | Jack | Queen | King | Ace deriving Show 
data JokerColor = Red | Black deriving Show 
data JCard = NormalCard Suit Rank | JokerCard JokerColor 

我怎麼能顯示JCard？目前我得到No instance for (Show JCard)

Answer 1

只需按照JokerColor的方法推導出JCard。

data JokerColor = Red | Black deriving Show 
data JCard = NormalCard Suit Rank | JokerCard JokerColor deriving Show 

對於大多數類型，人們通常派生Eq，Ord和Show。