haskell Data.Binary 示例

Question

我正在尝试序列化联系人类型，但我无法定义 put 和 get？

import Control.Monad
import Data.Binary

type Name = String
type Address = String

data Contacts = Contacts [(Name, Address)] deriving (Show)
instance Binary Contacts where
    put (Contacts [(n,a)]) = do ...
    get = do ...

main :: IO ()
main = do
    let c = Contacts [("gert","home")]
    let e = encode c
    let d = decode e
    print d

Answer 1

是的，您在定义 put 和 get 时遇到了困难。这能回答你的问题吗？

type Name = String
type Address = String

data Contacts = Contacts [(Name, Address)] deriving (Show)
instance Binary Contacts
    put (Contacts [(n,a)]) = do ...
    get = do ...

由于已经有实例:

instance (Binary a) => Binary [a]
instance (Binary a, Binary b) => Binary (a,b)
instance Binary Char

您应该能够轻松地提升底层的 put 和 get 例程:

instance Binary Contacts where
    put (Contacts set) = put set
    get = fmap Contacts get

因此，当您放置联系人时，您只需告诉它放置字符串对列表即可。当您想要反序列化联系人时，您只需获取基础列表并使用 Contacts 构造函数即可。