[Haskell-beginners] University project - weird problem

[Renato dos Santos Leal]

I've got a university project that demands me to do a program that receive a
.c file and analyze its syntax using haskell.
There are just a few things that I have to analyze:
literal strings, identifiers (in the program: identificadores), constants
(constantes), operators (operadores) and reserverd words(palavras
reservadas)

There are two major problems in the program:

(1) I've got this guard in le_bloco: | x `elem` listS = do separador (x:xs)
but it doesn't seem to work. Every time I enable it I recieve this in
execution time (after calling verifica)

ERROR - Cannot find "show" function for:
*** Expression : verifica
*** Of type    : IO a

So I've made one workaround that prints the separator but stops the
program...I guess the problem is doing the recursivity

(2) My second problem is: when I have one identifier or keyword alone in a
line or it's the last element of it it just won't print my coment!
this is the function:

pPCouI (x:xs) z
    | membroPC z = do{ putStr (z ++ " <palavra chave>\n") ; le_bloco (x:xs)}
    | otherwise = do{putStr z ; putStr " <identificador>\n" ; le_bloco
(x:xs)}

*Please help me solving those problems as soon as possible!*

Here is the whole program:

listO = ['+', '-', '*', '/', '%', '^', '=', '>', '<', '.', '|', '&', '!',
'~']
listS = [';', '{', '(', ')', '}', '[', ']', ',']
listC = ['0','1'..'9']
listCF = listC ++ ['.']
listA = listO ++ listS ++ [' ']
listPC =
["auto","double","int","struct","break","else","long","switch","case",

"enum","register","typedef","char","extern","return","union","const",

"float","short","unsigned","continue","for","signed","void","default",
          "goto","sizeof","volatile","do","if","static","while"]

verifica = do
    putStr ("Favor visualizar o codigo para ver os bugs e erros do
programa\n")
    putStr ("Digite o nome do arquivo de entrada: ")
    arqent <- getLine
    texto <- readFile arqent
    le_bloco texto

le_bloco (x:xs)
    | x `elem` listO = do operador (x:xs)
    | x `elem` listC = do cnum (x:xs)
  --  | x `elem` listS = do separador (x:xs)
    | x `elem` listS = do{ putStr[x] ; putStr " <separador>\n" }
    | x == '"' = litstr (xs)
    | x /= ' ' = pchave (x:xs) []
    | x == ' ' = le_bloco xs
    | otherwise    = do { putStr "Outro\n" ; le_bloco xs }

separador (x:xs)
    | x `elem` listS = do{ putStr [x] ; separador xs}
    | otherwise = do{ putStr " <separador>\n" ; le_bloco xs}

cnum (x:xs)
    | x `elem` listCF = do{ putChar x ; cnum xs}
    | otherwise = do{ putStr " <cte. numerica>\n" ; le_bloco (x:xs)}

operador (x:xs)
    | x `elem` listO = do{ putChar x ; operador xs}
    | otherwise = do{ putStr " <operador>\n" ; le_bloco (x:xs)}

litstr (x:xs)
    | x /= '"' = do{ putChar x ; litstr xs}
    | otherwise = do{ putStr " <literal string>\n" ; le_bloco xs}

pchave (x:xs) ys
    | x `notElem` listA = pchave xs (ys++[x])
    | otherwise = pPCouI (x:xs) ys

pPCouI (x:xs) z
    | membroPC z = do{ putStr (z ++ " <palavra chave>\n") ; le_bloco (x:xs)}
    | otherwise = do{putStr z ; putStr " <identificador>\n" ; le_bloco
(x:xs)}

membroPC x
    | x `elem` listPC = True
    | otherwise = False

I'm sorry for the bad english, it's been a while since the last time i used
it =)
Ah, I'm just starting to learn Haskell, first time i've seen it was like a
month ago so pretend that I know nothing
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.haskell.org/pipermail/beginners/attachments/20100421/9d2c54b1/attachment.html