dedupe a list of lists in haskell without using nub

dedupe-nested-lists.hs

-- [[1,2],[2,3],[4,5]] becomes [[1,2],[3],[4,5]]
-- this file can be run using: `stack runghc dedupe-nested-lists.hs`

dedupe_against_self =
  foldr
    (\member memo ->
      if (any (== member) memo)
        then memo
        else member : memo)
    []

dedupe_against_memo memo = filter (\x -> not $ any (== x) memo)

dedupe_nested_lists lst =
  reverse $ foldl
    (\memo x ->
      let memo' = concat memo
          x' = dedupe_against_self x
          x'' = dedupe_against_memo memo' x'
      in
        x'' : memo)
    []
    lst

main = do
  let lst = dedupe_nested_lists [[1,2],[2,3],[4,5]]
  putStrLn $ show $ lst -- [[1,2],[3],[4,5]]