LaTeX 2 HTML, still updating

latex2html.hs

import Data.Tree
import Data.List
import Debug.Trace
import Maybe
--the last int is the amount of argument
data Label = Command String
  | Constant String
  | Declaration
  deriving Show

--commandType = 
cmdStopChar = [' ', '\\' ,'{', '}']
constStopChar = ['\\','}','{']
readCommand tex = '\\':takeWhile ((flip notElem) (cmdStopChar)) (tail tex)
readConstant = takeWhile ((flip notElem) constStopChar)
removeConstant t = drop (length (readConstant t)) t
removeCommand t = drop (length (readCommand t)) t

--returns [String]
tokenize [] = []
tokenize (x:xs)
  | (x == '}') || (x == '{')    = [x]:tokenize xs
  | (x == '\\')                 = (readCommand tex):(tokenize (removeCommand tex))
  | otherwise                   = (readConstant tex):(tokenize (removeConstant tex))
  where tex = (x:xs)

--returns (Forest, remaining)
--parseNode :: [String]->(Forest Label, [String])
parseNode lex
  | lex == []          = ([], [])
  | head lex == "}"    = ([], tail lex)
  | otherwise          = (headNode:tailNode, remainLex)
  where (headNode, tailLex) = sequenceNode lex
        (tailNode, remainLex) = (parseNode tailLex)

--return (Node, remaining)
sequenceNode (x:xs)
  | head x == '\\'    = (Node (Command (tail x)) [], xs)
  | head x == '{'     = (Node Declaration forest, remaining)
  | otherwise         = (Node (Constant x) []  , xs)
  where lex = (x:xs)
        (forest, remaining) = parseNode xs

--input Forest->Forest
commandTree ((Node (Command x) z):xs) = 
  --Find the maximum amount of parameters of x
  --k of them are possible if and only if 
  (Node (Command x) ( z ++ parm)):(commandTree rest)
  where (parm, rest) = commandTree' (parameterCount x) xs
commandTree (x:xs) = x:(commandTree xs)
commandTree [] = []

--commandTree' :: Int ->Forest Label->(Forest Label, Forest Label)
commandTree' count ((Node (Declaration) z):xs)
  | count > 0 = ((Node (Declaration) (commandTree z)):parm, rest)
  | otherwise = ([], xs)
  where (parm, rest) = commandTree' (count-1) xs
commandTree' _ x = ([], x)

cmd x  = Maybe.fromMaybe (\z -> "[ERROR:"++x++"]"++(compile z)++"[/ERROR]") $ (lookup x cmdList)

--compile :: Forest Label -> String
compile (x:xs) = (eval x) ++ compile (xs)
compile [] = ""

--eval :: Tree Label -> String
eval (Node (Command x) subtrees) = cmd x subtrees
eval (Node Declaration subtrees) = compile subtrees
eval (Node (Constant x) []) = x

plain ((Node (Command x) subtrees):xs) = "\\"++ x ++ (plain subtrees) ++ (plain xs)
plain ((Node (Constant x) []):xs) = x ++ (plain xs)
plain ((Node Declaration subtrees):xs) = "{" ++ (plain subtrees) ++ "}" ++ (plain xs)
plain [] = ""

latex2Html x = compile (commandTree (fst (parseNode (tokenize x))))

--List of commands--
cmdList = [("textbf",cmd_textbf),
           ("emph",cmd_emph),
           ("inlinemath",cmd_inlinemath)]

--parameterCounts :: String->Int
parameterCount x
  | elem x ["frac"]   = 2
  | elem x ["textbf","emph", "inlinemath"] = 1
  | otherwise       = 0

--The commands
cmd_textbf subtrees = "<strong>"++(compile subtrees)++"</strong>"
cmd_emph subtrees = "<emph>"++(compile subtrees)++"</emph>"
cmd_inlinemath subtrees = "$"++(plain (subForest (head subtrees)))++"$"