Cont.hs

emptyK :: r -> r
emptyK = id

myLength :: [a] -> (Int -> r) -> r
myLength xs k =
  case xs of
    []      -> k 0
    (_:xs') -> myLength xs' $ \n -> k (n+1)

ex1 = myLength [] emptyK
ex2 = myLength [1..10] emptyK

showLengths :: [[a]] -> (String -> r) -> r
showLengths xss k =
  case xss of
    []        -> k ""
    (xs:xss') -> myLength xs $ \n ->
                   showLengths xss' $ \s ->
                     k (show n ++ ", " ++ s)

ex3 = showLengths [[], [1..10]] emptyK