symbols = ['a'..'c']
--expand s = [c : s | c <- symbols]
--expand s = map (\c -> c : s) symbols
expand s = map (:s) symbols
palindrome s = s == reverse s

bfs init expand isGoal = search [init]
  where
    search [] = []
    search frontiera = let
      current = head frontiera in
      (if isGoal current then [current] else []) ++
         search (tail frontiera ++ expand current)

palindromes = bfs "" expand palindrome


lista = ["un", "sir", "ceva", "", "nevid", "", "", "ser"]


--nevide = filter (\s -> not (null s)) lista
--nevide = filter (\s -> not $ null s) lista
--nevide = filter (\s -> not . null $ s) lista
nevide = filter (not . null) lista

--inc x = x + 1
--inc x = (+1) x
inc = (+1) -- definiție point-free

--paren s = "(" ++ s ++ ")"
--paren s = ("("++) ( (++")") s)
paren = ("("++) . (++")") -- definiție point-free - ilizibilă

-- Pun în paranteze toate șirurile nevide:
--transform lista = map paren (filter (not . null) lista)
transform = map paren . filter (not . null)


-- Transpusa unei matrice:
-- Racket: apply map list M

matrix = [[1,2,3], [4,5,6], [7,8,9], [0,1,2]]

transpose m = 
  foldr
{-  (\ row transp ->
      zipWith (:) row transp
    ) -}
    (zipWith (:)) -- definiție point-free
    (map (\_ -> []) $ head m)
	m

-- alternativ
{-	(map (:[]) $ last m)
    $ take (length m - 1) m
-}



















tWith = flip map . filter (not . null)

tParen = (`tWith` paren)
tPrefix = (`tWith` (">>>"++))