{-# LANGUAGE DeriveDataTypeable, FlexibleInstances #-} 

module ToXml where

import Data.Typeable(Typeable)
import Data.Data(Data, showConstr, toConstr, gmapQ)

-- import qualified Text.XML.Expat.Tree as XML
-- Cheap drop-in replacement:
data XMLNode tag text = XMLElement tag [(tag, text)] [XMLNode tag text] 

instance Show (XMLNode String a) where
  show (XMLElement t _ cs) = "<"++ t++ ">"++ concatMap show cs ++ "</"++t ++">"

toXml :: (Data a)=> a-> XMLNode String String
toXml a = XMLElement (showConstr (toConstr a)) [] (gmapQ toXml a)

data Gubbins = Ho | Hi Int Gubbins deriving (Typeable, Data)

-- Das geht nicht:
{-
data X = X (Int-> String) deriving (Typeable, Data)
-}