Question

I have a fully functional redact program written in haskell.it replaces all the words that you input with starts.However i have a problem with the command line arguments.
If you type in:

cat poem.txt | redact word1 word2 word3

it only redacts word1

if you write

cat poem.txt | redact “word1 word2 word3”

it redacts all 3 words…this is probably some kind of mistake i did with the command line arguments…here is my code

module Main where

import System
import Data.Char
import Data.Bits

convertWord :: Eq a=> [a] -> String
convertWord = map (const '*')

lowercase :: [Char]->[Char]
lowercase ch = map toLower ch

redact :: String -> String -> String
redact text keywords = unlines(map unwords redactedtext)
         where redactedtext = map processed text1
               text1        = map words (lines text)
               processed    = map tobeconverted
               keywords1    = words keywords
               tobeconverted x | lowercase x `elem` map lowercase keywords1     =   convertWord x
                               | otherwise                                      = x


main = do
   text <- getContents
   (key:_) <- getArgs
   let   
          result = redact text key




   putStr (result)

Answer 1

The point is this:

(key:_) <- getArgs

Here you explicitly ignore everything but the first argument.

If redact function would take a list of keywords, you could just pass through the whole list of arguments you get from getArgs:

keys <- getArgs
let result = redact text keys

Note that this way, your redact function actually gets a bit easier, because you do not have to split words.
In addition, you whole program gets safer, because it does not abort when no arguments are given.