Counts line indents in code and shows stats

indentcount.hs

-- @author silverweed, 2016
-- @license WTFPL
import System.Environment
import System.IO
import Data.List

showIndents input = header ++ (mkList input) ++ "\n"
                    where
                    header = "indent: occurrences\n"
                    mkList = intercalate "\n" . map (\(o,i) -> (show i) ++ ": " ++ (show o)) .
                             map (\l -> (length l, head l)) . group . sort . buildIndents .
                             filter (\x -> length x > 0) . lines

buildIndents = map indents
               where
               indents = length . takeWhile (== '\t')

printAllIndents []    = return ()
printAllIndents files = readAll files >>= putStrLn . showIndents
                        where
                        readAll [] = return ""
                        readAll (file:files) = do s  <- readFile file
                                                  ss <- readAll files
                                                  return $ s ++ ss

main = getArgs >>= \x -> case length x of
                         0 -> interact showIndents
                         _ -> printAllIndents x