Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org
You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than "Re: Contents of Beginners digest..." Today's Topics: 1. Re: Parsec chapter in realworldhaskell (ch.16) (Benjamin Edwards) 2. Re: first open source haskell project and a mystery to boot (Alia) 3. Re: first open source haskell project and a mystery to boot (Alia) 4. help me with eroor (kolli kolli) 5. Re: help me with eroor (Daniel Fischer) 6. Re: help me with eroor (kolli kolli) 7. Re: help me with eroor (Daniel Fischer) 8. Re: help me with eroor (Brent Yorgey) ---------------------------------------------------------------------- Message: 1 Date: Fri, 14 Oct 2011 11:03:12 +0100 From: Benjamin Edwards <edwards.b...@gmail.com> Subject: Re: [Haskell-beginners] Parsec chapter in realworldhaskell (ch.16) To: Obscaenvs <obscae...@gmail.com> Cc: beginners@haskell.org Message-ID: <CAN6k4nh_GMenwsCL=7pwn2-gboma7mdnixnyq69ssu+jr5e...@mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" It's not that it has no effect. If you have two parsers that have no common initial productions then wrapping the first parser would have no effect. That is the case here. Just think of try as wrapping the stream / parser in a transaction. On failure it rolls back. On 14 Oct 2011 10:32, "Obscaenvs" <obscae...@gmail.com> wrote: > In http://book.realworldhaskell.org/read/using-parsec.html , under the > heading "Extended example: Full CSV Parser", there is in the function > quotedChar an occurrence of the operator <|> with a try after it (i.e. to > the right) . Now, in this chapter it says a little before that "try only > has an effect if it is on the left of a <|>.". So in this particular case, > try has no effect, or? > > The offending code: <code>quotedChar = noneOf "\"" <|> try (string "\"\"" > >> return '"')</code> > > Help much appreciated, if not absolutely vital :) > > /Fredrik > > _______________________________________________ > Beginners mailing list > Beginners@haskell.org > http://www.haskell.org/mailman/listinfo/beginners > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/beginners/attachments/20111014/4258c87f/attachment-0001.htm> ------------------------------ Message: 2 Date: Fri, 14 Oct 2011 08:12:58 -0700 (PDT) From: Alia <alia_kho...@yahoo.com> Subject: Re: [Haskell-beginners] first open source haskell project and a mystery to boot To: "dmcbr...@neondsl.com" <dmcbr...@neondsl.com> Cc: "beginners@haskell.org" <beginners@haskell.org> Message-ID: <1318605178.19185.yahoomail...@web65711.mail.ac4.yahoo.com> Content-Type: text/plain; charset=iso-8859-1 David McBride wrote: > Sorry, it is the id3 function.? I'm not sure if the code ever worked, > or if you are using it in a way that was not intended by the writer. > It is because somehow xs because empty while attrs is not empty, then > it tries to take the head of an empty list.? If you know what it > should be doing well enough, you could fix it by giving it a valid > case for when: > id3 atts [] = .... > Unfortunately I have no idea how this id3 function is supposed to work. No worries. I appreciate you taking the time to have a look at this in any case. Best, AK ------------------------------ Message: 3 Date: Fri, 14 Oct 2011 08:37:19 -0700 (PDT) From: Alia <alia_kho...@yahoo.com> Subject: Re: [Haskell-beginners] first open source haskell project and a mystery to boot To: "beginners@haskell.org" <beginners@haskell.org> Message-ID: <1318606639.86380.yahoomail...@web65714.mail.ac4.yahoo.com> Content-Type: text/plain; charset=iso-8859-1 Brent Yorgey wrote: > It must be a problem with the ID3 implementation itself.? 'items' is > obviously not empty.? So the error must be coming from one of the > calls to 'head' in the ID3 implementation (of which there are > several).? The original author (whoever they were) ought to be ashamed > of him/herself.? Having bugs in your implementation is excusable, but > using functions like 'head' which can crash is not! ;)? Thanks for confirming this. I think it's best not to waste any more time on this. I appreciate your help in any case, AK ------------------------------ Message: 4 Date: Fri, 14 Oct 2011 13:59:22 -0600 From: kolli kolli <nammukoll...@gmail.com> Subject: [Haskell-beginners] help me with eroor To: beginners@haskell.org Message-ID: <CAE7D9k4G8FQDUBMgcCOq1=mkhferwcydl6xg3xsrfna-di2...@mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" import Text.ParserCombinators.Parsec csvFile = endBy line eol line = sepBy cell (char ',') cell = many (noneOf ",\n") eol = char '\n' parseCSV :: String -> Either ParseError [[String]] parseCSV input = parse csvFile "(unknown)" input *showing error: <interactive>:1:32: Not in scope: `main' * -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/beginners/attachments/20111014/be160744/attachment-0001.htm> ------------------------------ Message: 5 Date: Fri, 14 Oct 2011 22:08:21 +0200 From: Daniel Fischer <daniel.is.fisc...@googlemail.com> Subject: Re: [Haskell-beginners] help me with eroor To: beginners@haskell.org Message-ID: <201110142208.21519.daniel.is.fisc...@googlemail.com> Content-Type: Text/Plain; charset="utf-8" On Friday 14 October 2011, 21:59:22, kolli kolli wrote: > import Text.ParserCombinators.Parsec > > csvFile = endBy line eol > line = sepBy cell (char ',') > cell = many (noneOf ",\n") > eol = char '\n' > > parseCSV :: String -> Either ParseError [[String]] > parseCSV input = parse csvFile "(unknown)" input > > *showing error: > <interactive>:1:32: Not in scope: `main' > * If you don't have a module declaration in your file, it is assumed to be module Main (main) where thus, if there's no main function, compilation fails. Include a module declaration in your file, module Whatever (parseCSV, csvFile, line, cell, eol) where (the export list is optional, if you omit it, all top-level declarations are exported). ------------------------------ Message: 6 Date: Fri, 14 Oct 2011 14:49:04 -0600 From: kolli kolli <nammukoll...@gmail.com> Subject: Re: [Haskell-beginners] help me with eroor To: Daniel Fischer <daniel.is.fisc...@googlemail.com> Cc: beginners@haskell.org Message-ID: <cae7d9k5xw7v-ey48f_ma9zjffqw_1cqj-z7qbn550p4pj9u...@mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" namratha@ubuntu:~/Desktop$ runghc Main.hs <interactive>:1:32: Not in scope: `main' On Fri, Oct 14, 2011 at 2:45 PM, kolli kolli <nammukoll...@gmail.com> wrote: > I am using ubuntu..i am running it in the terminal window.... > > > On Fri, Oct 14, 2011 at 2:36 PM, Daniel Fischer < > daniel.is.fisc...@googlemail.com> wrote: > >> On Friday 14 October 2011, 22:26:45, you wrote: >> > i gave >> > module Main(csvFile, line) where >> > import Text.ParserCombinators.Parsec >> > >> > csvFile = endBy line eol >> > line = sepBy cell (char ',') >> > cell = many (noneOf ",\n") >> > eol = char '\n' >> > >> > parseCSV :: String -> Either ParseError [[String]] >> > parseCSV input = parse csvFile "(unknown)" input >> > >> > its giving me the same error >> >> Did you try to run main from the ghci prompt? >> The file loads without problems here. >> >> > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/beginners/attachments/20111014/c45b8434/attachment-0001.htm> ------------------------------ Message: 7 Date: Fri, 14 Oct 2011 23:13:57 +0200 From: Daniel Fischer <daniel.is.fisc...@googlemail.com> Subject: Re: [Haskell-beginners] help me with eroor To: kolli kolli <nammukoll...@gmail.com> Cc: beginners@haskell.org Message-ID: <201110142313.57685.daniel.is.fisc...@googlemail.com> Content-Type: Text/Plain; charset="utf-8" On Friday 14 October 2011, 22:49:04, kolli kolli wrote: > namratha@ubuntu:~/Desktop$ runghc Main.hs > > <interactive>:1:32: Not in scope: `main' Yes, runghc needs a main function. Load the file in ghci to try out normal functions. ------------------------------ Message: 8 Date: Fri, 14 Oct 2011 18:35:41 -0400 From: Brent Yorgey <byor...@seas.upenn.edu> Subject: Re: [Haskell-beginners] help me with eroor To: beginners@haskell.org Message-ID: <20111014223541.ga1...@seas.upenn.edu> Content-Type: text/plain; charset=us-ascii By the way, if you need a CSV parser, there are several already on Hackage: 'csv' [1] is the simplest; for more sophisticated uses there are also bytestring-csv [2] and csv-enumerator [3]. But perhaps you are just writing a CSV parser in order to learn Parsec; in which case, by all means carry on! -Brent [1] http://hackage.haskell.org/package/csv [2] http://hackage.haskell.org/package/bytestring-csv [3] http://hackage.haskell.org/package/csv-enumerator On Fri, Oct 14, 2011 at 01:59:22PM -0600, kolli kolli wrote: > import Text.ParserCombinators.Parsec > > csvFile = endBy line eol > line = sepBy cell (char ',') > cell = many (noneOf ",\n") > eol = char '\n' > > parseCSV :: String -> Either ParseError [[String]] > parseCSV input = parse csvFile "(unknown)" input > > *showing error: > <interactive>:1:32: Not in scope: `main' > * > _______________________________________________ > Beginners mailing list > Beginners@haskell.org > http://www.haskell.org/mailman/listinfo/beginners ------------------------------ _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 40, Issue 20 *****************************************