RLE

gistfile1.hs

import Data.List (group)

rle:: String -> [(Char, Int)]
rle []        = error "Empty List"
rle [x]       = [(x, 1)]
rle st@(x:xs) = (head start, cnt) : rle ending where
            start = takeWhile (==x) st
            cnt = length start
            ending = drop cnt st


-- with library
rle2:: String -> [(Char, Int)]
rle2 = map (\g -> (head g, length g)) . group