Aneto wrote:
compress :: Eq a => [a] -> [(a, Int)] If you have string "AAABCCC" it transforms it to : {A, 3} {B,1} {C,3}
Basically you need to "group" equal elements of the list first and then transform every group (which is a list of equal elements) to the tuple of (first_element , the_ length_of_the_group). All necessary functions can be found in Prelude and Data.List: import Data.List compress :: Eq a => [a] -> [(a, Int)] compress xs = map (\g -> (head g, length g)) (group xs) PS You can express it somehow nicer with arrows thought: import Data.List import Control.Arrow compress :: Eq a => [a] -> [(a, Int)] compress = map (head &&& length) <<< group -- View this message in context: http://old.nabble.com/Help-to-solve-simple-problem-%21-tp26249028p26294356.h... Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.