如何在Haskell中返回一个元组

Question

type Record=([Char],[Char],[Char],[Char],[Char])

createAccount::IO()->Record
createAccount=do
    putStrLn "Enter First Name"
    fname<-getLine
    putStrLn "Enter Last Name"
    lname<-getLine
    putStrLn "Enter State"
    state<-getLine
    putStrLn "Enter City"
    city<-getLine
    putStrLn "Enter House No."
    hnum<-getLine
    let hnumInt = read hnum :: Integer
    putStrLn "Enter Contact"
    contact<-getLine
    return (fname,lname,state,city,contact)

Answer 1

错误消息是说类型签名createAccount实际上是:

createAccount :: IO ([Char],[Char],[Char],[Char],[Char])

不像IO() -> Record你宣布的那样.

修复它的选项:

• 更改类型签名IO ([Char],[Char],[Char],[Char],[Char])(或equivalenly: IO Record)
• 删除类型签名 - 你不需要它,因为Haskell可以解决它.