Haskell 中“putStrLn”的基本错误。 VScode 扩展 Haskelly

Question

main = do line <- getLine
        let line' = reverse line
        putStrLn $ "You said " ++ line' ++ " backwards!"
        putStrLn $ "Yes, you really said " ++ line ++ " backwards!"

错误：

$ stack runhaskell "c:\Users\FruitfulApproach\Desktop\Haskell\test.hs"

C:\Users\FruitfulApproach\Desktop\Haskell\test.hs:4:5: error:
    parse error on input `putStrLn'
  |
4 |     putStrLn $ "You said " ++ line' ++ " backwards!"
  |     ^^^^^^^^

我也尝试过在缩进行上使用单个制表符。

这是我的制表符 -> 空格设置：

我也试过重新启动 VSCode。

提前致谢！

Answer 1

我认为您的代码缩进不够。试试这个：

main = do line <- getLine
          let line' = reverse line
          putStrLn $ "You said " ++ line' ++ " backwards!"
          putStrLn $ "Yes, you really said " ++ line ++ " backwards!"

具体来说，do 之后的行应与其后的行一样缩进，即 line <- getLine.

Haskell 中“putStrLn”的基本错误。 VScode 扩展 Haskelly

Basic error with `putStrLn` in Haskell. VScode extension Haskelly

haskell

visual-studio-code

haskell-stack