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Today's Topics:
1. Re: parsec and source material with random order lines
(Emmanuel Touzery)
2. Re: parsec and source material with random order lines
(Dudley Brooks)
----------------------------------------------------------------------
Message: 1
Date: Tue, 25 Dec 2012 09:15:51 +0100
From: Emmanuel Touzery <[email protected]>
Subject: Re: [Haskell-beginners] parsec and source material with
random order lines
To: "[email protected]" <[email protected]>
Message-ID:
<cac42rekbfom2-kvexv3tbqzle6lnb8uzjmx8bghigrnn35z...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
I think you are right, this is probably the right track. A little more
googling with permutation parsers gave me this, which is also about parsing
iCal using parsec:
http://stackoverflow.com/questions/3706172/haskell-parsec-and-unordered-properties
I'll review all this and see if that solves the problem... Thank you!
Emmanuel
On Tue, Dec 25, 2012 at 3:28 AM, Brent Yorgey <[email protected]>wrote:
> Hi Emmanuel,
>
> Sounds like you want a permutation parser, perhaps? Check out
>
>
> http://hackage.haskell.org/packages/archive/parsec/latest/doc/html/Text-Parsec-Perm.html
>
> -Brent
>
> On Tue, Dec 25, 2012 at 12:18:37AM +0100, Emmanuel Touzery wrote:
> > Hi,
> >
> > I'm trying to parse ical files but the source material doesn't matter
> > much. First, I know there is an icalendar library on hackage, but I'm
> > trying to learn as well through this.
> >
> > Now the format is really quite simple and actually I'm parsing it, it
> > works, but I don't like the code I'm writing, it feels wrong and I'm sure
> > there is a better way. Actually for now I'm parsing it to an array of
> > arrays, but I want to fill a proper "data" structure.
> >
> > For my purpose the file contains a bunch of records like this:
> >
> > BEGIN:VEVENT
> > DTSTART:20121218T103000Z
> > DTEND:20121218T120000Z
> > [..]
> > DESCRIPTION:
> > [..]
> > END:VEVENT
> >
> > There are a bunch of records I don't care about and also I want to parse
> no
> > matter what is the order of directives (so, i want to parse also if DTEND
> > appears before DTSTART for instance, and so on).
> >
> > That last part is my one problem. I can't do:
> >
> > parseBegin
> > start <- parseStart
> > end <- parseEnd
> > skipRows
> > desc <- parseDesc
> > skipRows
> > end <- parseEnd
> > return Event { eventStart = start, eventEnd = end ...}
> >
> > my current working code is:
> >
> > parseEvent = do
> > parseBegin
> > contents <- many1 $ (try startDate)
> > <|> (try endDate)
> > <|> (try description)
> > <|> unknownCalendarInfo
> > parseEnd
> > return contents
> >
> > But then contents of course returns an array, while I want to return only
> > one element here.
> >
> > SOMEHOW what I would like is:
> >
> > parseEvent = do
> > parseBegin
> > contents <- many1 $ (start <- T.try startDate)
> > <|> (end <- T.try endDate)
> > <|> (desc <- T.try description)
> > <|> unknownCalendarInfo
> > parseEnd
> > return Event { eventStart = start, eventEnd = end ...}
> >
> > But obviously as far as Parsec is concerned startDate could occur
> several
> > times and also it's just not valid Haskell syntax.
> >
> > So, any hint about this problem? Parsing multi-line records with Parsec,
> > when I don't know the order in which the lines will appear? I mean sure I
> > can convert my array to the proper data structure... I find which element
> > in the array contains the start date and then which contains the end
> > date... and build my data structure.. But I'm sure something much nicer
> can
> > be done... I just can't find how.
> >
> > I see the author of iCalendar fixed the problem but I can't completely
> > understand his source, it's too many things at the same time for me, I
> need
> > to take this one step at a time.
> >
> > Thank you!
> >
> > Emmanuel
>
> > _______________________________________________
> > Beginners mailing list
> > [email protected]
> > http://www.haskell.org/mailman/listinfo/beginners
>
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
>
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------------------------------
Message: 2
Date: Tue, 25 Dec 2012 01:20:59 -0800
From: Dudley Brooks <[email protected]>
Subject: Re: [Haskell-beginners] parsec and source material with
random order lines
To: "[email protected]" <[email protected]>
Message-ID: <[email protected]>
Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
I think you are right, this is probably the right track. A little more
googling with permutation parsers gave me this, which is also about
parsing iCal using parsec:
http://stackoverflow.com/questions/3706172/haskell-parsec-and-unordered-properties
I'll review all this and see if that solves the problem... Thank you!
Emmanuel
On Tue, Dec 25, 2012 at 3:28 AM, Brent Yorgey <[email protected]
<mailto:[email protected]>> wrote:
Hi Emmanuel,
Sounds like you want a permutation parser, perhaps? Check out
http://hackage.haskell.org/packages/archive/parsec/latest/doc/html/Text-Parsec-Perm.html
-Brent
On Tue, Dec 25, 2012 at 12:18:37AM +0100, Emmanuel Touzery wrote:
> Hi,
>
> I'm trying to parse ical files but the source material doesn't
matter
> much. First, I know there is an icalendar library on hackage, but I'm
> trying to learn as well through this.
>
> Now the format is really quite simple and actually I'm parsing
it, it
> works, but I don't like the code I'm writing, it feels wrong and
I'm sure
> there is a better way. Actually for now I'm parsing it to an array of
> arrays, but I want to fill a proper "data" structure.
>
> For my purpose the file contains a bunch of records like this:
>
> BEGIN:VEVENT
> DTSTART:20121218T103000Z
> DTEND:20121218T120000Z
> [..]
> DESCRIPTION:
> [..]
> END:VEVENT
>
> There are a bunch of records I don't care about and also I want
to parse no
> matter what is the order of directives (so, i want to parse also
if DTEND
> appears before DTSTART for instance, and so on).
>
> That last part is my one problem. I can't do:
>
> parseBegin
> start <- parseStart
> end <- parseEnd
> skipRows
> desc <- parseDesc
> skipRows
> end <- parseEnd
> return Event { eventStart = start, eventEnd = end ...}
>
> my current working code is:
>
> parseEvent = do
> parseBegin
> contents <- many1 $ (try startDate)
> <|> (try endDate)
> <|> (try description)
> <|> unknownCalendarInfo
> parseEnd
> return contents
>
> But then contents of course returns an array, while I want to
return only
> one element here.
>
> SOMEHOW what I would like is:
>
> parseEvent = do
> parseBegin
> contents <- many1 $ (start <- T.try startDate)
> <|> (end <- T.try endDate)
> <|> (desc <- T.try description)
> <|> unknownCalendarInfo
> parseEnd
> return Event { eventStart = start, eventEnd = end ...}
>
> But obviously as far as Parsec is concerned startDate could
occur several
> times and also it's just not valid Haskell syntax.
>
> So, any hint about this problem? Parsing multi-line records with
Parsec,
> when I don't know the order in which the lines will appear? I
mean sure I
> can convert my array to the proper data structure... I find which
element
> in the array contains the start date and then which contains the end
> date... and build my data structure.. But I'm sure something much
nicer can
> be done... I just can't find how.
>
> I see the author of iCalendar fixed the problem but I can't
completely
> understand his source, it's too many things at the same time for
me, I need
> to take this one step at a time.
>
> Thank you!
>
> Emmanuel
> _______________________________________________
> Beginners mailing list
> [email protected] <mailto:[email protected]>
> http://www.haskell.org/mailman/listinfo/beginners
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