从数据类型打印列表

Question

我正在研究一种数据类型，它涉及一个人的名字和姓氏、他们的方向和他们居住的城市。我制作了一个函数来打印这个，但我很确定我可以以某种方式实例化 Show 或创建另一个 class 并实例化它。我有一个名为 Direction:

的数据类型

type Direction = (Person, Dir, City) 
type Name = String
type Surname = String
type City = String
data Person = Per Name Surname
data Dir = Street String Int | House String

这两个元素：

dirJon:: Direction
dirJon = (Per "Jon" "Prieto", House "Enea", "Orio")
dirMiren:: Direction
dirMiren = (Per "Miren" "Artola", Street "Aldamar" 15, "Donostia")

所以我想出的函数是：

write:: [Direction] -> IO() 
write [] = return ()
write ((Per a b,Street c d, e):cs) = do
                                     putStrLn ( a ++ ' ': b)
                                     putStrLn ("c/" ++ c ++'c':show d)
                                     putStrLn e
                                     write cs
write ((Per a b,House c, e):cs) = do
                                     putStrLn ( a ++ ' ': b)
                                     putStrLn ("House " ++ c)
                                     putStrLn e
                                     write cs

这会导致正确的实现，这意味着如果我调用 write [dirJon,dirMiren] 会正确打印：

Jon Prieto
casa Enea
Orio
Miren Artola
c/Aldamarc15
Donostia

（换句话说，我不想把它写成论文）

所以如果有人能帮助我以某种方式制作它的实例，因为我已经尝试制作一个使用 [Direction] 作为参数的 class 但是因为它是 type 而不是数据我做不到。

Answer 1

您不能为类型别名定义实例。我只想定义一个合适的数据类型。

type Name = String
type Surname = String
type City = String
data Person = Per Name Surname
data Location = Street String Int | House String 
data Address = Address Person Location City

addrJon, addrMiren :: Address
dirJon = Address (Per "Jon" "Prieto") (House "Enea") "Orio"
dirMiren = Address (Per "Miren" "Artola") (Street "Aldamar" 15) "Donostia"

instance Show Person where
    show (Per x y) = x ++ " " ++ y

instance Show Location where
    show (Street name number) = "c/" ++ name ++ "c" ++ show number
    show (House name) = "House " ++ name

instance Show Address where
    show (Address p l c) = show p ++ "\n" ++ show l ++ "\n" ++ c

write :: [Address] -> IO() 
write [] = return ()
write (a:as) = putStrLn (show a) >> write as
-- write = traverse print

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