module ListUtils
( pad_left_to,
  pad_right_to,
  splitWith
) where


-- Stolen from ByteString. Splits a list at each element satisfying
-- the predicate p.
splitWith :: (a -> Bool) -> [a] -> [[a]]
splitWith p xs =
    ys : case zs of
           []   -> []
           _:ws -> splitWith p ws
    where (ys,zs) = break p xs


-- Pads a list (on the left) to length len by prepending pad_elem.
pad_left_to :: Int -> a -> [a] -> [a]
pad_left_to len pad_elem xs =
     if (length xs) >= len then
         xs
     else
         (replicate padcount pad_elem) ++ xs
         where
           padcount = len - (length xs)


-- Pads a list (on the right) to length len by appending pad_elem.
pad_right_to :: Int -> a -> [a] -> [a]
pad_right_to len pad_elem xs =
     if (length xs) >= len then
         xs
     else
         xs ++ (replicate padcount pad_elem)
         where
           padcount = len - (length xs)