Line / Whitespace selection tool

sel.hs

import System.IO
import System.Environment
import Text.Printf
import Data.Char
import Data.Set
import Data.List
import Text.Regex
import Text.Regex.Posix

printList :: [String] -> IO ()
printList [] = return ()
printList (a:rs) = do putStrLn a
                      printList rs

incr :: Int -> [Int]
incr x = (x : incr (x + 1))

filterIdx :: Set Int -> [a] -> [a]
filterIdx set lis = snd . unzip $ Prelude.filter (\x -> member (fst x) set)
                                                 (zip (incr 1) lis)

formatLines :: [[String]] -> [String]
formatLines lines = Prelude.map (\line ->
    Prelude.foldl (\x y -> y ++ x) "" (intersperse " " (reverse line))) lines

printCols :: Set Int -> IO ()
printCols set = do
  cont <- getContents
  printList . formatLines $ Prelude.map ((filterIdx set) . words) (lines cont)
  return ()
    
printLines :: Set Int -> IO ()
printLines set = do
  cont <- getContents
  printList (filterIdx set (lines cont))

type SelArguments = (Bool, [Int])

parseArgs' :: [String] -> SelArguments -> SelArguments
parseArgs' [] res = res
parseArgs' (h:hs) (col, ls) =
  if h =~ "-c|--col(umns?)?" then parseArgs' hs (True, ls)
  else if h =~ "[0-9]+" then parseArgs' hs (col, (read h) : ls)
    else error "Cannot parse arguments"

parseArgs :: [String] -> SelArguments
parseArgs arr = parseArgs' arr (False, [])

main :: IO ()
main = do
  args <- getArgs
  let pargs = (parseArgs args) in
    case pargs of
      (col, list) -> let intSet = (fromList list) in
        case col of
          True -> printCols intSet
          False -> printLines intSet
  return ()