在Haskell中使用streamly在后台运行REPL

Question

我正在尝试使用

streamly-process

与后台的一些 REPL 进行通信。它可以是 Python 或任何东西，但在这里我尝试运行 GHCi。我想出了以下代码：

import Data.Word
import qualified Streamly.Data.Stream.Prelude as Stream
import qualified Streamly.Data.Fold.Prelude as Fold
import qualified Streamly.System.Process as Process
import qualified Streamly.Console.Stdio as Stdio
import qualified Streamly.Data.Array.Foreign as Array


stringToByteArray :: String -> Array.Array Word8
stringToByteArray = Array.fromList . map (fromIntegral . fromEnum)

-- a version of getLine that does not ignore the newline character.
getNewLn :: IO String
getNewLn =  fmap (++ "\n") getLine


main :: IO ()
main = do
    Stream.fold (Fold.takeEndBy ( == stringToByteArray "Leaving GHCi.") Stdio.writeChunks) $
        Process.pipeChunks "ghci" [] $
          fmap stringToByteArray $
            Stream.repeatM getNewLn
            -- When using Stream.fromList, it works ! To do so, uncomment the following :

            -- Stream.fromList ["putStrLn \"This works ! \"\n", " 3 + 4\n"]

当我使用

fromList

时，它按预期工作并返回：

GHCi, version 9.8.2: https://www.haskell.org/ghc/  :? for help
ghci> This works ! 
ghci> 7
ghci> Leaving GHCi.

但是，当我使用

getNewLn

时，这就是我得到的：

GHCi, version 9.8.2: https://www.haskell.org/ghc/  :? for help
ghci> I'm typing
the return key
several times
but nothing happens ...

我做错了什么？

Answer 1

输入在 pipelineChunks 的输入端得到缓冲。一旦缓冲区中收集到足够数量的输入，它将实际发送到进程（此处为 ghci）。可以通过在 pipelineChunks 实现中应用行缓冲来解决。