run length encoding on haskell

runLengthEncoding.hs

import Data.List (group)
import Control.Arrow

main = putStrLn answer
solve = concatMap (uncurry (:) . (head &&& show.length)) . group
answer = solve "aaaabb"

runLengthEncoding2.hs

module RunLengthEncoding where

import Data.List (group)
import Control.Arrow ((&&&))

main :: IO ()
main = putStrLn (runLengthEncoding "aaaabb")

-- runLengthEncoding
-- runLengthEncodingは、Stringを受け取り、Run-Length EncodingしたStringを返却する
-- @param: String
-- @returns: String
runLengthEncoding :: String -> String
runLengthEncoding = concatMap encodingMap . group

encodingMap :: [Char] -> [Char]
encodingMap = (uncurry addList . encoding)

-- addList
-- addListは、要素とListを受け取り、結合したListを返却する
-- @param: a
-- @param: [a]
-- @returns: [a]
addList :: a -> [a] -> [a]
addList = (:)

encoding :: [c] -> (c, String)
encoding = (head &&& show.length)