[Haskell-beginners] University project - weird problem

[Renato dos Santos Leal]

Thank you Stephen!

Yes, I'm using hugs. My teacher told me to use it and he corrects our
projects using it, the differece between hugs and GHC, is it large?

I don't know if I got what you meant with pure functions, but I'll keep
studying.

2010/4/21 Stephen Blackheath [to Haskell-Beginners] <
mutilating.cauliflowers.stephen at blacksapphire.com>

> Renato,
>
> All I did was I added type signatures to your code, and it worked.  It is a
> very good idea to put type signatures on all top-level functions, otherwise
> you can get confusing errors.
>
> It looks like you are using Hugs - It is much better to use GHC.  That's
> what everyone uses now.
>
> Another thing:  For a program this size it doesn't matter much, but in
> Haskell we always try to make our functions pure if we can (that is, not IO
> type).  Then you get the best advantage out of using Haskell.
>
>
> Steve
>
>
> 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 :: IO ()
>
> 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 :: String -> IO ()
>
> 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 :: String -> IO ()
>
> separador (x:xs)
>    | x `elem` listS = do{ putStr [x] ; separador xs}
>    | otherwise = do{ putStr " <separador>\n" ; le_bloco xs}
>
> cnum :: String -> IO ()
>
> cnum (x:xs)
>    | x `elem` listCF = do{ putChar x ; cnum xs}
>    | otherwise = do{ putStr " <cte. numerica>\n" ; le_bloco (x:xs)}
>
> operador :: String -> IO ()
>
> operador (x:xs)
>    | x `elem` listO = do{ putChar x ; operador xs}
>    | otherwise = do{ putStr " <operador>\n" ; le_bloco (x:xs)}
>
> litstr :: String -> IO ()
>
> litstr (x:xs)
>    | x /= '"' = do{ putChar x ; litstr xs}
>    | otherwise = do{ putStr " <literal string>\n" ; le_bloco xs}
>
> pchave :: String -> String -> IO ()
>
> pchave (x:xs) ys
>    | x `notElem` listA = pchave xs (ys++[x])
>    | otherwise = pPCouI (x:xs) ys
>
> pPCouI :: String -> String -> IO ()
>
> 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 :: String -> Bool
>
> membroPC x
>    | x `elem` listPC = True
>    | otherwise = False
>
>
> Renato dos Santos Leal wrote:
>
>> 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
>>
>>
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> Beginners mailing list
>> Beginners at haskell.org
>> http://www.haskell.org/mailman/listinfo/beginners
>>
>
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