在haskell-pipes中分流流动流

本文介绍了在haskell-pipes中分流流动流的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 我无法通过haskell-pipes来管理流水线。基本上，我分析了一堆文件，然后我必须以人性化的方式将结果打印到终端上 > 将结果编码为JSON 所选路径取决于命令行选项。 在第二种情况下，我必须输出一个前括号，然后输入每个输入值，后跟一个逗号，然后输入一个右括号。目前 insertCommas 永不终止，因此不会输出右括号。 导入管道导入Data.ByteString.Lazy为B 导入Data.Aeson（编码） insertCommas :: Consumer B.ByteString IO（） insertCommas = do先< - 等待抬起$ B.putStr首先 for cat $ \obj - >提升$ do putStr， B.putStr obj jsonExporter :: Consumer（FilePath，AnalysisResult）IO（） jsonExporter = do lift $ putStr[ P.map encode> - > insertCommas lift $ putStr] exportStream :: Config - > Consumer（FilePath，AnalysisResult）IO（） exportStream conf = case outputMode conf JSON - > jsonExporter _ - > P.map（export conf）> - > P.stdoutLn main :: IO（） main = do - 前两行是Docopt的东西，不相关 args< - parseArgsOrExit模式=<< getArgs ins let conf = readConfig args runEffect $ each ins > - > P.mapM分析> - > P.map（filterResults conf）> - > P.filter filterNulls > - > exportStream conf 解决方案我认为你应该'管道' -组。它有一个插入，但不是散布者，但是写出来并不是什么大不了的事。我认为，您应该远离消费者端，以解决这类问题。 { - ＃LANGUAGE OverloadedStrings＃ - } 导入管道导入合格的Pipes.Prelude作为P 导入合格的Data.ByteString.Lazy.Char8作为B 导入Pipes.Group 导入Lens.Simple - 或Control.Lens或Lens.Micro或任何视图/ ^。 import System.Environment intersperse_ :: Monad m => a - >制片人a m r - > Producer amr intersperse_ a producer = intercalates（yield a）（producer ^。chunksOf 1） main = do args< - getArgs let op prod = json的案例参数：_ - >产量[*> intersperse_，prod< * yield] _ - > intersperse_prod runEffect $ op生产者> - > P.mapM_ B.putStr putStrLn其中 producer = mapM_ yield（B.wordsthis is a test） 给我这个 >>> ：main json [this，is，a，test] >>> ：main --- 这是一个测试 I'm having trouble directing flow though a pipeline with haskell-pipes. Basically, I analyze a bunch of files and then I have to eitherprint results to the terminal in a human-friendly wayencode results to JSONThe chosen path depends upon a command line option.In the second case, I have to output an opening bracket, then every incoming value followed by a comma and then a closing bracket. Currently insertCommas never terminates, so the closing bracket is never outputted.import Pipesimport Data.ByteString.Lazy as Bimport Data.Aeson (encode)insertCommas :: Consumer B.ByteString IO ()insertCommas = do first <- await lift $ B.putStr first for cat $ \obj -> lift $ do putStr "," B.putStr objjsonExporter :: Consumer (FilePath, AnalysisResult) IO ()jsonExporter = do lift $ putStr "[" P.map encode >-> insertCommas lift $ putStr "]"exportStream :: Config -> Consumer (FilePath, AnalysisResult) IO ()exportStream conf = case outputMode conf of JSON -> jsonExporter _ -> P.map (export conf) >-> P.stdoutLnmain :: IO ()main = do -- The first two lines are Docopt stuff, not relevant args <- parseArgsOrExit patterns =<< getArgs ins <- allFiles $ args `getAllArgs` argument "paths" let conf = readConfig args runEffect $ each ins >-> P.mapM analyze >-> P.map (filterResults conf) >-> P.filter filterNulls >-> exportStream conf 解决方案 I think you should 'commify' with pipes-group. It has an intercalates, but not an intersperse, but it's not a big deal to write. You should stay away from the Consumer end, I think, for this sort of problem.{-#LANGUAGE OverloadedStrings #-}import Pipesimport qualified Pipes.Prelude as Pimport qualified Data.ByteString.Lazy.Char8 as Bimport Pipes.Groupimport Lens.Simple -- or Control.Lens or Lens.Micro or anything with view/^.import System.Environmentintersperse_ :: Monad m => a -> Producer a m r -> Producer a m rintersperse_ a producer = intercalates (yield a) (producer ^. chunksOf 1) main = do args <- getArgs let op prod = case args of "json":_ -> yield "[" *> intersperse_ "," prod <* yield "]" _ -> intersperse_ " " prod runEffect $ op producer >-> P.mapM_ B.putStr putStrLn "" where producer = mapM_ yield (B.words "this is a test")which give me this >>> :main json [this,is,a,test] >>> :main --- this is a test 这篇关于在haskell-pipes中分流流动流的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！