-- | This module contains additional utility functions for list.

module Extended.Data.List
       ( removeAt
       , removeAtMultiple
       ) where

import           Universum

-- | Removes element from list by given index. If there's
-- no element at such index then list returns unchanged.
removeAt :: Int -> [a] -> [a]
removeAt i l | i < 0 = l
removeAt i l = case after of
                     []       -> l
                     (_:rest) -> before ++ rest
  where (before, after) = splitAt i l

-- | Like 'removeAt' but takes list of indices to remove.
removeAtMultiple :: [Int] -> [a] -> [a]
removeAtMultiple indices = map snd
                         . filter ((`notElem` indices) . fst)
                         . zip [0..]