用parsec解析递归数据

import Data.Attoparsec.Text.Lazy
import Data.Text.Lazy.Internal (Text)
import Data.Text.Lazy (pack)

data List a = Nil | Cons a (List a)

list :: Text
list = pack $ unlines
  [ "0"
  , "1"
  , "2"
  , "5"
  ]

How can List Int可以实现解析器来解析Cons 0 (Cons 1 (Cons 2 (Cons 5 Nil))) from list?

ps: 纯解析器，不解析 a[Int]并将其转换为List Int是优选的。

像这样：

import Control.Applicative
-- rest of imports as in question

data List a = Nil | Cons a (List a)
  deriving Show -- for testing

-- definition of list as in question

parseList :: Parser (List Int)
parseList = foldr Cons Nil <$> many (decimal <* endOfLine)

在 GHCi 中测试：

*Main> parse parseList list
Done "" Cons 0 (Cons 1 (Cons 2 (Cons 5 Nil)))