在Haskell中创建数据类型

Question

我想创建一个新的数据类型，该数据类型可以使用Start或A tuple of values。 这就是我所拥有的：

type Coord = (Int, Int)
data Direction = N | E | S | W
                 deriving (Eq, Show, Read)


type Move = (Coord, Direction)
type BoardSpec = [(Coord, Bool)]

type GameTreeNode = (GameTree2, BoardSpec, Move)
data GameTree2 = Start | GameTreeNode deriving(Show)


blahblah :: GameTree2
blahblah = blahb

blahb :: GameTreeNode
blahb = (Start, testbo, ((1, 1), N))

但是，这给了我错误

Couldn't match type `(GameTree2, Move)' with `GameTree2'
Expected type: GameTree2
  Actual type: GameTreeNode

Answer 1

数据GameTree2 =开始| GameTreeNode派生（显示）

扩展为：

 
 
 
  
  data GameTree2 = Start | (GameTree2, BoardSpec, Move) deriving(Show)
 
  

您不能使元组成为您类型的有效值。

---

您需要将其包装在构造函数中：

 data GameTree2 = Start | Node GameTreeNode deriving(Show) 

Node是您为其选择的任何名称。