import Data.Char (intToDigit)
import DList

showInt :: Int -> DList Char
showInt n | n < 10 = singleton (intToDigit n)
showInt n | otherwise = showInt (n  `div` 10) +++ showInt (n `mod` 10)

go :: [Int] -> DList Char
go [] = empty
go (x:xs) =  showInt x +++ singleton ' ' +++ go xs

doIt :: [Int] -> String
doIt xs = fromDList (go xs)