gistfile1.hs

sumOfLastTwo xs = iter xs 0 0
    where iter xs s1 s2 = case xs of
                            []     -> s1 + s2
                            (y:ys) -> iter ys s2 y
                    
removeSuccessiveDuplicate xs = reverse (iter xs [])
    where iter ori rst = case ori of
                           []     -> rst
                           (x:xs) -> case rst of
                                       (y:_)
                                           | x==y      -> iter xs rst
                                           | otherwise -> iter xs (x:rst)
                                       [] -> iter xs (x:rst)

takeWhile condition list = reverse (iter condition list [])
    where iter condition ori rst =
              case ori of
                [] -> rst
                (x:xs) | condition x -> iter condition xs (x:rst)
                       | otherwise   -> rst