Haskell语言学习笔记（75）Conduit

安装 conduit

$ cabal install conduit
Installed conduit-1.3.0.3
Prelude> import Conduit
Prelude Conduit>

Conduit

Conduit 是一个处理流的库。

Prelude Conduit> :{
Prelude Conduit|   print $ runConduitPure
        $ yieldMany [1..10]
       .| mapC (+ 1)
       .| sinkList
Prelude Conduit| :}
[2,3,4,5,6,7,8,9,10,11]

应用实例

{-# LANGUAGE ExtendedDefaultRules #-}
import Conduit

magic :: Int -> IO Int
magic x = do
    putStrLn $ "I'm doing magic with " ++ show x
    return $ x * 2

main :: IO ()
main = do
    putStrLn "List version:"
    mapM magic (take 10 [1..]) >>= mapM_ print . takeWhile (< 18)
    putStrLn ""
    putStrLn "Conduit version:"
    runConduit
          $ yieldMany [1..]
         .| takeC 10
         .| mapMC magic
         .| takeWhileC (< 18)
         .| mapM_C print

List version:
I'm doing magic with 1
I'm doing magic with 2
I'm doing magic with 3
I'm doing magic with 4
I'm doing magic with 5
I'm doing magic with 6
I'm doing magic with 7
I'm doing magic with 8
I'm doing magic with 9
I'm doing magic with 10
2
4
6
8
10
12
14
16

Conduit version:
I'm doing magic with 1
2
I'm doing magic with 2
4
I'm doing magic with 3
6
I'm doing magic with 4
8
I'm doing magic with 5
10
I'm doing magic with 6
12
I'm doing magic with 7
14
I'm doing magic with 8
16
I'm doing magic with 9