haskell 。 WAI 简单 Web 应用程序出现问题(解压字节串)

Question

对字符串和文本进行了大量的打包、解包等操作，但仍然卡住了， 目标很简单，就像连接额外的请求信息的 hello world 一样:

{-# LANGUAGE OverloadedStrings #-}
import Network.Wai
import Network.Wai.Handler.Warp (run)
import Network.HTTP.Types (statusOK)
import qualified Data.ByteString.Lazy as L
import Data.ByteString.Char8 (unpack)
import qualified Data.Text.Lazy as T

application req = do
  return $ responseLBS statusOK [("Content-Type", "text/plain")]
    $ L.pack $  "Hello World" ++ (unpack $ rawPathInfo req)

main = run 3000 application

产生:

Couldn't match expected type `GHC.Word.Word8'
           against inferred type `Char'
      Expected type: [GHC.Word.Word8]
      Inferred type: [Char]
    In the second argument of `(++)', namely
        `(unpack $ rawPathInfo req)'
    In the second argument of `($)', namely
        `"Hello World" ++ (unpack $ rawPathInfo req)

急切需要提示如何使其工作。

Answer 1

使用 Data.ByteString.Lazy.Char8.pack 而不是 L.pack。