小编tom*_*lak的帖子

我想写一个简单的游戏“猜数字” -n尝试。我想添加一些条件和命中。是否可以在block内使用守卫do？

这是我的代码：

game = return()
game n = do putStrLn "guess number: 0-99"
            number<-getLine
            let y = read number
            let x =20
            | y>x = putStrLn "your number is greater than x"
            | y<x = putStrLn "your number is less than x"
            | y==x  putStrLn "U win!!"
            | otherwise = game (n-1)

已经出错

error: parse error on input ‘|’

它可以用一些空白来修复，还是不可能做到？

我试图检查树是否是另一棵树的子树。这是我的树数据：

data Tree a = Empty | Node a (Tree a)(Tree a) deriving Show

tree1 :: Tree Int
tree1 = Node 1
        (Node 2
          (Node 4 Empty Empty)
          (Node 5 Empty
              (Node 8 Empty Empty))
        )
        (Node 3
          (Node 6 Empty
           (Node 9 Empty Empty))
           (Node 7 Empty Empty)
          )

tree2 :: Tree Int
tree2 = Node 2
        (Node 4 Empty Empty)
        (Node 5 Empty
            (Node 8 Empty Empty))

最后定义未实现的功能：

isSubTree :: Eq a => Tree a -> Tree a …