Haskell 如何将IO字符串转换为代数类型的数据；产品“；一个txt文件？

我必须要求用户在Products.txt中输入产品的代码、名称和价格

produtoPath::FilePath
produtoPath = "Products.txt"

 adicionaProd::IO()
 adicionaProd = do
    putStr "Product's Code:"
    cod<-getLine
    putStr "Product's Name:"
    nom<-getLine
    putStr "Product's Price:"
    pre<-getLine
--  appendFile produtoPath
    putStr "Do you want to add some other product?"
    resp <- getLine
    if ((resp == "y")) then adicionaProd else return()

之后，我必须使用函数loadProducts加载产品。。。它读取上一个函数的文件，并返回类型IO Products，以便用户能够以类型Products的格式可视化文件中的内容

loadTable:: IO Produtos
loadTable = do
         s<-readFile produtoPath
    --   return generateList (map words)

loadTable:：IO产品
loadTable=do
s您可能需要从
adicionaProd
返回输入数据。因此，它的类型必须是

type Products   = [(Code, Name, Price)]
adicionaProd :: IO Products

然后，调整代码本身

 adicionaProd = do
    putStr "Product's Code:"
    cod<-getLine
    putStr "Product's Name:"
    nom<-getLine
    putStr "Product's Price:"
    pre<-getLine
    let prod :: (Code, Name, Price)
        prod = (read cod, nom, read pre)
    putStr "Do you want to add some other product?"
    resp <- getLine
    if resp == "y" then do
       rest <- adicionaProd 
       return (prod : rest)
    else 
       return [prod]

adicionaProd=do
PUTSR“产品代码：”
代码尝试使用
show:：show a=>a->String
将
[（代码、名称、价格）]
转换为
String
，并使用
read:：read a=>String->a
将
String
转换为
[（代码、名称、价格）]
 adicionaProd = do
    putStr "Product's Code:"
    cod<-getLine
    putStr "Product's Name:"
    nom<-getLine
    putStr "Product's Price:"
    pre<-getLine
    let prod :: (Code, Name, Price)
        prod = (read cod, nom, read pre)
    putStr "Do you want to add some other product?"
    resp <- getLine
    if resp == "y" then do
       rest <- adicionaProd 
       return (prod : rest)
    else 
       return [prod]