word length count

string.hs

import System.Environment (getArgs)
import Data.List (sortBy,sort, group)
import Data.Ord (comparing)
import Data.Char (toLower, isLetter)
import qualified Data.HashMap.Strict as HM

createReport :: Int -> String -> String
createReport n  =
    unlines 
    . map (\(w,count) -> w ++ " " ++ show count) 
    . take n
    . sortBy (flip $ comparing snd)
    . HM.toList 
    . HM.fromListWith (+)
    . map (\w -> (w, 1)) 
    . words 
    . map rnl

    
main = getArgs >>= \[nstr] -> interact (createReport (read nstr))

-- unicode avoidance: 
rnl :: Char -> Char
rnl = \c -> case c of 
  'a' -> 'a'
  'b' -> 'b'
  'c' -> 'c'
  'd' -> 'd'
  'e' -> 'e'
  'f' -> 'f'
  'g' -> 'g'
  'h' -> 'h'
  'i' -> 'i'
  'j' -> 'j'
  'k' -> 'k'
  'l' -> 'l'
  'm' -> 'm'
  'n' -> 'n'
  'o' -> 'o'
  'p' -> 'p'
  'q' -> 'q'
  'r' -> 'r'
  's' -> 's'
  't' -> 't'
  'u' -> 'u'
  'v' -> 'v'
  'w' -> 'w'
  'x' -> 'x'
  'y' -> 'y'
  'z' -> 'z'
  'A' -> 'a'
  'B' -> 'b'
  'C' -> 'c'
  'D' -> 'd'
  'E' -> 'e'
  'F' -> 'f'
  'G' -> 'g'
  'H' -> 'h'
  'I' -> 'i'
  'J' -> 'j'
  'K' -> 'k'
  'L' -> 'l'
  'M' -> 'm'
  'N' -> 'n'
  'O' -> 'o'
  'P' -> 'p'
  'Q' -> 'q'
  'R' -> 'r'
  'S' -> 's'
  'T' -> 't'
  'U' -> 'u'
  'V' -> 'v'
  'W' -> 'w'
  'X' -> 'x'
  'Y' -> 'y'
  'Z' -> 'z'
  _ -> '\n'--