title: How to convert list to string?
body: <p>I make a function which read file and removes in every line all the words that were encountered earlier in the same line.</p>
  
  <pre><code>{-# OPTIONS_GHC -Wall #-}
  module Main where
  import System.Environment
  import System.IO()
  
  main :: IO ()
  main = do args &lt;- getArgs 
            if (length args &gt; 0) then do
              f &lt;- get args
              putStrLn (seqWord $ head f)
            else do
              f &lt;- getContents
              putStrLn (seqWord f)
  
  get :: [String] -&gt; IO[String]
  get [] = return []
  get (file:xs) = do
    contents &lt;- readFile file
    fs &lt;- get xs
    return (contents:fs)
  
  seqWord :: String -&gt; String
  seqWord s = show (map (filterWord . words) (lines s))
  
  filterWord :: [String] -&gt; [String]
  filterWord [] = []
  filterWord (x:xs) = x : filterWord (filter(/=x) xs)
  </code></pre>
  
  <p>In answer I have list of lists, like this</p>
  
  <pre><code>[["1","12","5","8","13","145","85"],["546","822","1","12","58","8","9"]]
  </code></pre>
  
  <p>Please, help me fix this problem. Thank you</p>