Haskell输入并将值传递给函数

Question

putStrLn "Enter the Artist Name"
    art <- getLine
putStrLn "Enter the Number of CD's"
    num <- getLine

let test= buyItem currentStockBase art num
    printListIO (showcurrentList test)

我必须为buyItem传递的值是

buyItem currentStockBase "Akon" 20

但我想发送"Akon"到艺术和20我想发送num

它给了我这个错误

ERROR file:.\Project2.hs:126 - Type error in application
*** Expression     : buyItem currentStockBase art num
*** Term           : num
*** Type           : [Char]
*** Does not match : Int

请帮我

Answer 1

num是一个String.buyItem期待一个Int.您需要将String转换为Int,例如使用read.

buyItem currentStockBase art (read num)

编辑:String意味着[Char]---希望这意味着错误信息现在对你更有意义.