Haskell - “”do“结构中的最后一个语句必须是表达式” [英] Haskell -- "The last statement in a 'do' construct must be an expression"

问题描述

正如标题中所说： 构造中的最后一个语句必须是表达式的意思？我用 putStrLn 来结束我的 do 块，就像我在前面看到的几个示例中显示的那样，并且出现错误。

代码：

  main = do args<  -  getArgs 
 file< -readFile" TWL06.txt
 putStrLn结果
  

大多数情况下，这是因为你的代码是错误对齐的，编译器会认为你的do块过早地结束了（或者有额外的代码不属于那里）。 $ b

Like it says in the title: What does The last statement in a 'do' construct must be an expression mean? I ended my do block with a putStrLn like it shows in several examples I've seen, and i get an error.

Code:

main = do args <- getArgs
           file <-readFile "TWL06.txt"
           putStrLn results

解决方案

Most of the time, it's because your code is mis-aligned and compiler assumes that your "do" block ended prematurely (or has extra code that dont really belong there)

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