小编ric*_*k8r的帖子

当给定由\n分隔的文本输入文件时,此程序产生我期望的输出:

import System.IO

main :: IO ()
main = do h <- openFile "test.txt" ReadMode 
          xs <- getlines h
          sequence_ $ map putStrLn xs

getlines :: Handle -> IO [String]
getlines h = hGetContents h >>= return . lines

用withFile代替openFile并稍微重新排列

import System.IO

main :: IO ()
main = do xs <- withFile "test.txt" ReadMode getlines
          sequence_ $ map putStrLn xs

getlines :: Handle -> IO [String]
getlines h = hGetContents h >>= return . lines  

我设法完全没有输出.我很难过.

编辑:不再难过了:感谢一个人和所有人的深思熟虑和发人深省的答案.我在文档中做了一些阅读,并了解到withFile可以理解为支架 …