Haskell中带参数的I/O函数的正确类型

我想实现一个函数，根据性别提出不同的问题。但是我没有给它正确的类型

askDifferentQuestion :: String -> IO String
askDifferentQuestion sex = do
  putStrLn "ciao"

main = do
  sex <- getLine
  askDifferentQuestion sex

为什么我做错了？

putStrLn的类型是String->IO not String->IO String。

putStrLn的类型是String->IO not String->IO String。

类型IO String表示运行时生成字符串的输入/输出操作。按原样，askDifferentQuestion会导致，这通常表示一个不重要的值。这是因为要运行的唯一操作是类型为IO的putStrLn，也就是说，您运行它只是为了它的副作用

假设您的类型正确，请更改askDifferentQuestion的定义，以提示用户并返回响应。比如说

askDifferentQuestion :: String -> IO String
askDifferentQuestion sex = putStrLn (q sex) >> getLine
  where q "M" = "What is the airspeed velocity of an unladen swallow?"
        q "F" = "How do you like me now?"
        q "N/A" = "Fuzzy Wuzzy wasn’t fuzzy, was he?"
        q "N" = "Why do fools fall in love?"
        q "Y" = "Dude, where’s my car?"
        q _ = "Why do you park on a driveway and drive on a parkway?"

IO字符串类型表示在运行时生成字符串的输入/输出操作。按原样，askDifferentQuestion会导致，这通常表示一个不重要的值。这是因为要运行的唯一操作是类型为IO的putStrLn，也就是说，您运行它只是为了它的副作用

假设您的类型正确，请更改askDifferentQuestion的定义，以提示用户并返回响应。比如说

askDifferentQuestion :: String -> IO String
askDifferentQuestion sex = putStrLn (q sex) >> getLine
  where q "M" = "What is the airspeed velocity of an unladen swallow?"
        q "F" = "How do you like me now?"
        q "N/A" = "Fuzzy Wuzzy wasn’t fuzzy, was he?"
        q "N" = "Why do fools fall in love?"
        q "Y" = "Dude, where’s my car?"
        q _ = "Why do you park on a driveway and drive on a parkway?"

---

... 因此，askDifferentQuestion的类型是askDifferentQuestion:：String->IO。。。。因此，askDifferentQuestion的类型是askDifferentQuestion:：String->IO。在这种情况下，可以做的一件事是省略askDifferentQuestion的类型声明，然后使用：t命令询问ghci它自动推断的类型。在这种情况下，可以做的一件事是省略askDifferentQuestion的类型声明askDifferentQuestion，然后使用：t命令询问ghci自动推断的类型。