xml haskell

xml.hs

import System.Environment
import Data.List

type AttrName = String
type AttrVal = String
newtype TagName = TagName String deriving (Show)

data Attr = Attr AttrName AttrVal

listToStr :: (Show a) => [a] -> String
listToStr = (intercalate " ") . (map show)

instance Show Attr where
    show (Attr k v) = k ++ "=\"" ++ v ++ "\""

data Tag =
      Fragment [Tag]
    | Tag TagName [Attr] [Tag]

_IDENT = "    "

instance Show Tag where
    show (Tag (TagName a) attrs children) = openTag ++ identChild ++ closeTag
        where attrStr = listToStr attrs
              openTag = "<" ++ a ++ " " ++ attrStr ++ ">" ++ maybeNl
              maybeNl = if length childStr == 0 then "" else "\n"
              closeTag = "</" ++ a ++ ">\n"
              identChild = unlines $ map (_IDENT ++) (lines childStr)
              childStr = foldl (++) "" childrenStrs
              childrenStrs = map show children

main = do
    -- [path] <- getArgs
    -- c <- readFile path
    -- let a = "beginning"
    --     result = a ++ c
    -- putStrLn result
    putStrLn $ show $ Tag (TagName "text") [Attr "witdh" "300", Attr "witdh" "300"] [
                Tag (TagName "animation") [Attr "attr" "x", Attr "witdh" "300"] [],
                Tag (TagName "animation") [Attr "attr" "x", Attr "witdh" "300"] [],
                Tag (TagName "animation") [Attr "attr" "x", Attr "witdh" "300"] [
                    Tag (TagName "animation") [Attr "attr" "x", Attr "witdh" "300"] [],
                    Tag (TagName "animation") [Attr "attr" "x", Attr "witdh" "300"] [],
                    Tag (TagName "animation") [Attr "attr" "x", Attr "witdh" "300"] []
                    ]
                ]