bracketmatcher.hs

import Text.ParserCombinators.Parsec (Parser, parse, many, string)

import Control.Monad (msum, forM_)

program :: Parser ()
program = do
    rbr <- opening
    many program
    string rbr

    return ()

opening :: Parser String
opening = msum
    [ string "(" >> return ")"
    , string "[" >> return "]"
    , string "{" >> return "}"
    ]

cases =
    [ "((()()))"
    , "([{}]{(){}})"
    , "([{]}{(){}})"
    ]

main = 
    cases `forM_` \line ->
        print (parse program "" line)