src/ListUtils.hs

   1 module ListUtils
   2 ( pad_left_to,
   3   pad_right_to,
   4   splitWith
   5 ) where
   6
   7
   8 -- Stolen from ByteString. Splits a list at each element satisfying
   9 -- the predicate p.
  10 splitWith :: (a -> Bool) -> [a] -> [[a]]
  11 splitWith p xs =
  12     ys : case zs of
  13            []   -> []
  14            _:ws -> splitWith p ws
  15     where (ys,zs) = break p xs
  16
  17
  18 -- Pads a list (on the left) to length len by prepending pad_elem.
  19 pad_left_to :: Int -> a -> [a] -> [a]
  20 pad_left_to len pad_elem xs =
  21      if (length xs) >= len then
  22          xs
  23      else
  24          (replicate padcount pad_elem) ++ xs
  25          where
  26            padcount = len - (length xs)
  27
  28
  29 -- Pads a list (on the right) to length len by appending pad_elem.
  30 pad_right_to :: Int -> a -> [a] -> [a]
  31 pad_right_to len pad_elem xs =
  32      if (length xs) >= len then
  33          xs
  34      else
  35          xs ++ (replicate padcount pad_elem)
  36          where
  37            padcount = len - (length xs)