[Haskell-cafe] Need help with learning Parsec

[Sai Hemanth K]

gettext =  (many1 $ noneOf "><") >>= (return . Body)

works for your case.



On Thu, Jul 19, 2012 at 6:37 PM, Christian Maeder
<Christian.Maeder at dfki.de>wrote:

> Am 19.07.2012 14:53, schrieb C K Kashyap:
>
>  Dear gentle Haskellers,
>>
>> I was trying to whet my Haskell by trying out Parsec today to try and
>> parse out XML. Here's the code I cam up with -
>>
>> I wanted some help with the "gettext" parser that I've written. I had to
>> do a dummy "char '  ') in there just to satisfy the "many" used in the
>> xml parser. I'd appreciate it very much if someone could give me some
>> feedback.
>>
>
> You don't want empty bodies! So use many1 in gettext.
>
>   gettext = fmap Body $ many1 $ letter <|> digit
>
> If you have spaces in your bodies, skip them or allow them with
> noneOf "<".
>
> HTH Christian
>
>
>>
>> data XML =  Node String [XML]
>>            | Body String deriving Show
>>
>> gettext = do
>>               x <- many (letter <|> digit )
>>               if (length x) > 0 then
>>                  return (Body x)
>>               else (char ' ' >> (return $ Body ""))
>>
>> xml :: Parser XML
>> xml = do {
>>            name <- openTag
>>          ; innerXML <- many innerXML
>>          ; endTag name
>>          ; return (Node name innerXML)
>>           }
>>
>> innerXML = do
>>           x <- (try xml <|> gettext)
>>           return x
>>
>> openTag :: Parser String
>> openTag = do
>>          char '<'
>>          content <- many (noneOf ">")
>>          char '>'
>>          return content
>>
>> endTag :: String -> Parser String
>> endTag str = do
>>          char '<'
>>          char '/'
>>          string str
>>          char '>'
>>          return str
>>
>> h1 = parse xml "" "<a>A</a>"
>> h2 = parse xml "" "<a><b>A</b></a>"
>> h3 = parse xml "" "<a><b><c></c></b></a>"
>> h4 = parse xml "" "<a><b></b><c></c></a>"
>>
>> Regards,
>> Kashyap
>>
>>
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>>
>
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