Question

这是the problem的要旨：

check_if_proceed configFolders = do
  let emacsdf = "/home/jacek/.emacs.d"
  traceM ("calling check_if_proceed " ++ show ("ccc",configFolders))
  exists <- doesDirectoryExist emacsdf
  symlink <- pathIsSymbolicLink emacsdf
  let confemp = configFolders == []
  let result = False
  if exists
    then do
    {
      if symlink
      then do
        {
          putStrLn ("This action will overwrite the existing symlink\n"++
                    "poinitng to " ++ "SOMEWHERE-FINISH ME\n\n" )
        }
      else do
        {
          putStrLn (emacsdf ++ " is not a symlink\n"++
                    "to use this utility, in your terminal do soemthing like:\n"++
                    "$ mv " ++ emacsdf ++ " " ++ emacsdf ++ "-alternative-config\n" ++
                    "exiting..." )
        }
    }
    else do
    {
      putStrLn ("no " ++ emacsdf ++ "found in your home folder")
      if confemp
      then do
        {
          putStrLn ("nor folders with the alternative emacs config\n" ++
                    "exiting..." )

        }
      else
        do {
          putStrLn "will try to symlink one of the found folders"
          }
    }

加分指示如何在其中添加return语句。

工作代码

此链接显示了一些工作代码，使我可以使用命令式样式探索问题空间。

Answer 1

您在putStrLn和if之间缺少line 31上的一个分号：

    ....
    else do
    {
      putStrLn ("no " ++ emacsdf ++ "found in your home folder")
    ;                                                            -- HERE
      if confemp
      then do
        {
          putStrLn ("nor folders with the alternative emacs config\n" ++
                    "exiting..." )

        }
    ....

要遵循的模板是

    do { ... ; ... ; ... }

大括号和分号将防止由于代码中的缩进（可能是由于制表符/空格问题）而引起的任何解析错误。

完全明确表示法在每个;块语句之间始终使用do。 if ... then ... else ...弥补了一个表达式/ do语句，即使它们分散在多行代码中。

Haskell-如何嵌套多个包含多个putStrLn满足条件的if语句

工作代码

1 个答案: