Simple parser for the Dyck language https://en.wikipedia.org/wiki/Dyck_language

Dyck.hs

{-# LANGUAGE TypeFamilies #-}
module Dyck where

import Control.Applicative hiding (many)
import Control.Monad
import Data.Void
import Text.Megaparsec
import Text.Megaparsec.Char

newtype Dyck = Some [Dyck]
  deriving Show

pDyck :: (Token s ~ Char, Stream s) => Parsec Void s Dyck
pDyck = Some <$> many (char '[' *> pDyck <* char ']')

showDyck :: Dyck -> String
showDyck (Some xs) = mconcat ["[" ++ w ++ "]" | w <- showDyck xs]