读取直到haskell中的流结束 [英] Read until end of stream in haskell

问题描述

我对Haskell还是很陌生，我想一直从控制台读取行，直到流结束，并输出大写形式的所有内容.到目前为止，我已经

I'm fairly new to Haskell, and I'd like to keep reading lines from the console until the end of the stream, and outputting everything I get in upper case. So far, I've got

import Data.Char

main = myLoop

myLoop = do inp <- getLine
            if (inp == "x") 
              then putStrLn "Bye!"
              else do putStrLn(map toUpper inp)
                      myLoop

但是，我似乎无法弄清楚如何避免if (inp == "x")条件并将其替换为流结束条件.

However, I can't seem to figure out how to avoid the if (inp == "x") condition and replace it with an end of stream condition.

简而言之，我正在寻找Haskell等效于C ++中的while (cin >> line)

In short, I'm looking for Haskell's equivalent to while (cin >> line) in C++

推荐答案

这超出了您真正要求的范围，但是我经常使用这种模式:interact:

This goes way beyond what you're really asking for, but I use this pattern a lot: interact:

myFun :: String -> String
myFun = ...

main = interact (unlines . myFun . lines)

将对标准输入的每一行执行您的函数myFun，并将结果发送到标准输出.

Your function myFun will be executed against every line of standard input and the result sent to standard output.

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