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-- ======================================================= --
-- Definition of set of operations with strings.
-- ======================================================= --
-- ------------------------------------------------------- --
-- Cleaning string.
cleaning :: String -> String
cleaning _ = []
-- ------------------------------------------------------- --


-- ------------------------------------------------------- --
-- Removing all symbols 'c' from string.
removing :: Char -> String -> String
removing _ [] = []
removing c (x:xs)
    | x == c = removing c xs
    | otherwise = x:removing c xs
-- ------------------------------------------------------- --


-- ------------------------------------------------------- --
-- Replacing all symbols 'cs' to symbol 'cd' in string.
replacing :: Char -> Char -> String -> String
replacing _  _ [] = []
replacing cs cd (x:xs)
    | x == cs = cd : replacing cs cd xs
    | otherwise = x : replacing cs cd xs
-- ------------------------------------------------------- --


-- ------------------------------------------------------- --
-- Append symbol 'c' to start of string.
adding :: Char -> String -> String
adding c s = c : s
-- ------------------------------------------------------- --


-- ======================================================= --
-- Declaration of type which describe string modification.
-- ======================================================= --
-- ------------------------------------------------------- --
-- Type of function which modify string.
type StringModifier = String -> String
-- ------------------------------------------------------- --


-- ======================================================= --
-- Definition of string modificators.
-- ======================================================= --
-- ------------------------------------------------------- --
-- Modification of string 's' by modifier.
process :: StringModifier -> String -> String
process func s = func (s)
-- ------------------------------------------------------- --


-- ------------------------------------------------------- --
-- Modificaton of string 's' by list of modifiers.
processAll :: [StringModifier] -> String -> String
processAll [] s = s
processAll (f:fs) s = processAll fs (f (s) )
-- ------------------------------------------------------- --


-- ------------------------------------------------------- --
-- Removing from string 'b' all symbols from string 'a'.
deleteAll :: String -> String -> String
deleteAll [] b = b
deleteAll a [] = []
deleteAll a b  = processAll removingList b
    where removingList = foldl (\acc m -> (removing (m) ):acc) [] a
-- ------------------------------------------------------- --



-- ======================================================= --
-- Main function.
-- ======================================================= --
-- ------------------------------------------------------- --
main = do {
    putStrLn (                  inputString);
    putStrLn (cleaning          inputString);
    putStrLn (removing  'S'     inputString);
    putStrLn (replacing 'S' 'X' inputString);
    putStrLn (adding    'A'     inputString);
    putStrLn (process cleaning  inputString);
    putStrLn (processAll [
                    removing 's',
                    removing 'S',
                    removing 'r',
                    replacing '_' ' ',
                    removing ' '
                    ]           inputString);
    putStrLn (deleteAll "aoei"  "boenairoes");
}   where inputString = "Input stRiNgg__ _ witH STrrange Sym123ol345..!"
-- ------------------------------------------------------- --