我在Haskell中創建了一個類型,但我不知道如何獲取我創建的類型的字段之一。我應該怎麼辦?我應該做一個功能Book -> String
或類似的東西?Haskell - 類型的訪問字段
import Data.List
import System.IO
type Book = (Int, String, String, String, String, String, String)
bookNew :: Int -> String -> String-> String -> String -> String -> String -> Book
bookNew isbn title author genre date publisher summary =
(isbn,title,author,genre,date,publisher,summary):: Book
main = do
let book = bookNew 1 "title" "author" "genre" "date" "publisher" "summary"
--Access title of "book" somehow
return book
甚至比類型同義詞是使用'newtype'讓'Title','Author','Genre'等無法代替使用彼此。 – cdk