Re: [Haskell-cafe] parsec: parserFail multiple error messages
The error message can be improved in your examples by using count 5 instead of many1. C. Am 08.08.2012 21:24, schrieb silly: I am trying to create a parsec parser that parses an integer and then checks if that integer has the right size. If not, it generates an error. I tried the following: 8--- import Text.Parsec import Text.Parsec.String integer :: Parser Int integer = do s - many1 digit let n = read s if n 65535 then parserFail integer overflow else return n 8--- The problem is that when I try this parse integer 7 I get the following error: Left (line 1, column 6): unexpected end of input expecting digit integer overflow ie there are three error messages but I only want the last one. Is there something I can do about this? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] parsec: parserFail multiple error messages
On Thu, Aug 9, 2012 at 3:59 AM, Christian Maeder christian.mae...@dfki.de wrote: The error message can be improved in your examples by using count 5 instead of many1. Yes, I know. That's what I ended up doing. But this is an ad hoc solution. I think parsec should offer a more general solution. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] parsec: parserFail multiple error messages
On 12-08-08 03:24 PM, silly wrote: The problem is that when I try this parse integer 7 I get the following error: Left (line 1, column 6): unexpected end of input expecting digit integer overflow ie there are three error messages but I only want the last one. Is there something I can do about this? import Text.Parsec import Text.Parsec.String integer :: Parser Int integer = try integ3r ? number at most 65535 integ3r = do s - many1 digit let n = read s if n 65535 then unexpected number overflow else return n main = do parseTest integer a7 parseTest integer 7 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] parsec: parserFail multiple error messages
I am trying to create a parsec parser that parses an integer and then checks if that integer has the right size. If not, it generates an error. I tried the following: 8--- import Text.Parsec import Text.Parsec.String integer :: Parser Int integer = do s - many1 digit let n = read s if n 65535 then parserFail integer overflow else return n 8--- The problem is that when I try this parse integer 7 I get the following error: Left (line 1, column 6): unexpected end of input expecting digit integer overflow ie there are three error messages but I only want the last one. Is there something I can do about this? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] parsec: parserFail multiple error messages
I found a similar question asked in June 2009 on the haskell-beginners archives, titled Clearing Parsec error messages. A hack that was proposed (http://www.haskell.org/pipermail/beginners/2009-June/001809.html) was to insert a dummy character into the stream, consume it, and then fail. Still, I'd like to see if there is a cleaner way to modify the error state in the Parsec monad. NIck On Wednesday, August 08, 2012 03:24:31 PM silly wrote: I am trying to create a parsec parser that parses an integer and then checks if that integer has the right size. If not, it generates an error. I tried the following: 8--- import Text.Parsec import Text.Parsec.String integer :: Parser Int integer = do s - many1 digit let n = read s if n 65535 then parserFail integer overflow else return n 8--- The problem is that when I try this parse integer 7 I get the following error: Left (line 1, column 6): unexpected end of input expecting digit integer overflow ie there are three error messages but I only want the last one. Is there something I can do about this? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] parsec: parserFail multiple error messages
Inserting a character into the stream can be expensive if for example the stream is a ByteString. I tried the following crazy solution and it seems that it works: succeed :: Parser () succeed = mkPT $ \st - return $ Consumed $ return $ Ok () st $ unknownError st succeed is a parser that always succeeds without really consuming any input but it also resets the error state. I really have no understating of how mkPT works. Can someone tell me if this is a bad idea? On Wed, Aug 8, 2012 at 4:09 PM, Nick Vanderweit nick.vanderw...@gmail.com wrote: I found a similar question asked in June 2009 on the haskell-beginners archives, titled Clearing Parsec error messages. A hack that was proposed (http://www.haskell.org/pipermail/beginners/2009-June/001809.html) was to insert a dummy character into the stream, consume it, and then fail. Still, I'd like to see if there is a cleaner way to modify the error state in the Parsec monad. NIck On Wednesday, August 08, 2012 03:24:31 PM silly wrote: I am trying to create a parsec parser that parses an integer and then checks if that integer has the right size. If not, it generates an error. I tried the following: 8--- import Text.Parsec import Text.Parsec.String integer :: Parser Int integer = do s - many1 digit let n = read s if n 65535 then parserFail integer overflow else return n 8--- The problem is that when I try this parse integer 7 I get the following error: Left (line 1, column 6): unexpected end of input expecting digit integer overflow ie there are three error messages but I only want the last one. Is there something I can do about this? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] parsec: parserFail multiple error messages
On Wed, Aug 8, 2012 at 8:26 PM, silly silly8...@gmail.com wrote: Inserting a character into the stream can be expensive if for example the stream is a ByteString. I tried the following crazy solution and it seems that it works: succeed :: Parser () succeed = mkPT $ \st - return $ Consumed $ return $ Ok () st $ unknownError st succeed is a parser that always succeeds without really consuming any input but it also resets the error state. Because you're using the 'Consumed' constructor, you're also telling parsec not the back-track if there any errors following this parsers. This means that 'succeed failingParser' won't backtrack, even if 'failingParser' doesn't consume input. Are you using your original parser within a larger parser? Are the error messages also not great? Antoine ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
