ybe? I'd like it very much if I could get
> > an example of a missed match by not using the complete match.
> >
> > regards,
> > Kashyap
> >
> > Sent from my Windows Phone
> > From: Roman Cheplyaka
> > Sent: 24/07/2013 8:19 PM
> > To: C K Kash
Thanks Kyle,
My initial implementation was evaluating the whole list - the current one
though just returns the first successful result. Anyway, I think I need the
backtracking - I would want the "aaa" as the result :)
I will now explore using go-routines to implement laziness.
Thank you so much
t use it like Maybe? I'd like it very much if I could get
> an example of a missed match by not using the complete match.
>
> regards,
> Kashyap
>
> Sent from my Windows Phone
> From: Roman Cheplyaka
> Sent: 24/07/2013 8:19 PM
> To: C K Kashyap
> Cc: Haskell Cafe
Because of laziness, you do in a sense only take the first successful
value. When I've made parser combinators for Python before, I've used
either generators or exceptions to get lazy evaluation, since computing the
whole list of possibilities for each bind would ruin the running time of
the algor
PM
To: C K Kashyap
Cc: Haskell Cafe
Subject: Re: [Haskell-cafe] Parsec question
Think about this: if you always take only the first element, why do you
need lists at all?
Roman
* C K Kashyap [2013-07-24 19:56:29+0530]
> Dear Cafe,
>
> I am trying to implement[1] parsec in go using the &
Think about this: if you always take only the first element, why do you
need lists at all?
Roman
* C K Kashyap [2013-07-24 19:56:29+0530]
> Dear Cafe,
>
> I am trying to implement[1] parsec in go using the "Monadic Parser
> Combinators" paper [2] . I've been able to implement "plus" "bind" and
Dear Cafe,
I am trying to implement[1] parsec in go using the "Monadic Parser
Combinators" paper [2] . I've been able to implement "plus" "bind" and
"many"
While doing the implementation - I looked at bind closely
bind :: Parser a -> (a -> Parser b) -> Parser b
p `bind` f = \inp -> concat [f v in
Maybe this is something you do not even want to use a parser combinator library
for. The package
http://hackage.haskell.org/packages/archive/list-grouping/0.1.1/doc/html/Data-List-Grouping.html
contains a function breakBefore, so you can write
main = do inp <- readFile ...
let
Carlo,
Thanks a lot! This looks very promising (though I have to test it for my
purpose more in depth). As you mention, the key seems to be the optionMaybe
combinator. Thanks for pointing to it.
Immanuel
2013/3/5 Carlo Hamalainen
> On Mon, Mar 4, 2013 at 1:44 AM, Immanuel Normann <
> immanuel
On Mon, Mar 4, 2013 at 1:44 AM, Immanuel Normann <
immanuel.norm...@googlemail.com> wrote:
> I am trying to parse a semi structured text with parsec that basically
> should identify sections. Each section starts with a headline and has an
> unstructured content - that's all.
>
Here's my attempt:
Andrey,
Thanks a lot for your effort! I have the same suspect that the lookahead in
the content parser is the problem, but I don't know how to solve it either.
At least the I learned from your code that noneOf is also a quite useful
parser in this context which I have overlooked.
Anyway, if you fin
Immanuel,
I tried but I couldn't figure it out. Here's a gist with my attempts and
results so far: https://gist.github.com/achudnov/f3af65f11d5162c73064
There, 'test' uses my attempt at specifying the parser, 'test2' uses
yours. Note that your attempt wouldn't parse multiple sections -- for
that yo
Andrey,
Thanks for your attempt, but it doesn't seem to work. The easy part is the
headline, but the content makes trouble.
Let me write the code a bit more explicit, so you can copy and paste it:
--
{-# LANGUAGE FlexibleContexts #-}
module Main where
im
Immanuel,
Since a heading always starts with a new line (and ends with a colon
followed by a carriage return or just a colon?), I think it might be
useful to first separate the input into lines and then classify them
depending on whether it's a heading or not and reassemble them into the
value
Hi,
I am trying to parse a semi structured text with parsec that basically
should identify sections. Each section starts with a headline and has an
unstructured content - that's all. For instance, consider the following
example text (inside the dashed lines):
---
top 1:
Antoine Latter wrote:
> On Sun, Oct 3, 2010 at 11:55 AM, Ben Franksen
> wrote:
>> Stephen Tetley wrote:
>>> Does this one give the "expected" error message for Parsec3.1 -
>>> unfortunately I can't test as I'm still using Parsec 2.1.0.1.
>>>
parser = block (many digit "digit")
>>
>> Unfortun
On Sun, Oct 3, 2010 at 11:55 AM, Ben Franksen wrote:
> Stephen Tetley wrote:
>> Does this one give the "expected" error message for Parsec3.1 -
>> unfortunately I can't test as I'm still using Parsec 2.1.0.1.
>>
>>> parser = block (many digit "digit")
>
> Unfortunately, no.
>
> Cheers
> Ben
>
He
Stephen Tetley wrote:
> Does this one give the "expected" error message for Parsec3.1 -
> unfortunately I can't test as I'm still using Parsec 2.1.0.1.
>
>> parser = block (many digit "digit")
Unfortunately, no.
Cheers
Ben
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Does this one give the "expected" error message for Parsec3.1 -
unfortunately I can't test as I'm still using Parsec 2.1.0.1.
> parser = block (many digit "digit")
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On Wed, Sep 29, 2010 at 1:01 PM, Daniel Fischer
wrote:
> On Wednesday 29 September 2010 19:10:22, Ben Franksen wrote:
>> >
>> > Note the last line mentions only '}'. I would rather like to see
>> >
>> > expecting "}" or digit
>> >
>> > since the parser could very well accept another digit here.
Christian Maeder wrote:
> Am 29.09.2010 20:01, schrieb Daniel Fischer:
>> On Wednesday 29 September 2010 19:10:22, Ben Franksen wrote:
Note the last line mentions only '}'. I would rather like to see
expecting "}" or digit
since the parser could very well accept anot
Am 29.09.2010 20:01, schrieb Daniel Fischer:
> On Wednesday 29 September 2010 19:10:22, Ben Franksen wrote:
>>>
>>> Note the last line mentions only '}'. I would rather like to see
>>>
>>> expecting "}" or digit
>>>
>>> since the parser could very well accept another digit here.
>
> parsec2 did
Antoine and Christian:
Many thanks for your help on this thread.
(I am still digesting it; much appreciated; will post when I get it working.)
-- Peter
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Daniel Fischer wrote:
> On Wednesday 29 September 2010 19:10:22, Ben Franksen wrote:
>> >
>> > Note the last line mentions only '}'. I would rather like to see
>> >
>> > expecting "}" or digit
>> >
>> > since the parser could very well accept another digit here.
>
> parsec2 did that, I don't kno
On Wednesday 29 September 2010 19:10:22, Ben Franksen wrote:
> >
> > Note the last line mentions only '}'. I would rather like to see
> >
> > expecting "}" or digit
> >
> > since the parser could very well accept another digit here.
parsec2 did that, I don't know whether that change is intention
Ben Franksen wrote:
>> import Control.Applicative ((*>),(<*))
>> import Text.Parsec
>> import Text.Parsec.Char
>> block p = char '{' *> p <* char '}'
>> parser = block (many digit)
>> main = parseTest parser "{123a}"
>
> gives the output
>
> parse error at (line 1, column 5):
> unexpected "a"
I have a question about Parsec. The following program
> import Control.Applicative ((*>),(<*))
> import Text.Parsec
> import Text.Parsec.Char
> block p = char '{' *> p <* char '}'
> parser = block (many digit)
> main = parseTest parser "{123a}"
gives the output
parse error at (line 1, column 5
Am 29.09.2010 11:55, schrieb Christian Maeder:
> Am 29.09.2010 09:54, schrieb Christian Maeder:
>> Am 29.09.2010 05:35, schrieb Peter Schmitz:
>> [...]
>>> Error parsing file: "...\sampleTaggedContent.txt" (line 4, column 1):
>>> unexpected end of input
>>> expecting "<"
>>>
>>> The input was:
>> [
Am 29.09.2010 09:54, schrieb Christian Maeder:
> Am 29.09.2010 05:35, schrieb Peter Schmitz:
> [...]
>> Error parsing file: "...\sampleTaggedContent.txt" (line 4, column 1):
>> unexpected end of input
>> expecting "<"
>>
>> The input was:
> [...]
>>
>>> -- Parsers:
>>> taggedContent = do
>>>opt
Am 29.09.2010 05:35, schrieb Peter Schmitz:
[...]
> Error parsing file: "...\sampleTaggedContent.txt" (line 4, column 1):
> unexpected end of input
> expecting "<"
>
> The input was:
[...]
>
>> -- Parsers:
>> taggedContent = do
>>optionalWhiteSpace
>>aTag
>>many tagOrContent
>>aTa
On Tue, Sep 28, 2010 at 10:35 PM, Peter Schmitz wrote:
> I am a new Parsec user, and having some trouble with a relatively
> simple parser.
>
> The grammar I want to parse contains tags (not html) marked by
> angle brackets (e.g., ""), with arbitrary text (no angle
> brackets allowed) optionally i
I am a new Parsec user, and having some trouble with a relatively
simple parser.
The grammar I want to parse contains tags (not html) marked by
angle brackets (e.g., ""), with arbitrary text (no angle
brackets allowed) optionally in between tags.
Tags may not nest, but the input must begin and en
Am Samstag 18 April 2009 01:33:44 schrieb Michael P Mossey:
> I've just about got this parser working, but wondering about something.
> Turns out I need "try" inside the "lookahead" here.
>
> parseText :: Parser String
> parseText = manyTill anyChar $ lookAhead (try (string "//"))
>
> Without try,
I've just about got this parser working, but wondering about something. Turns
out I need "try" inside the "lookahead" here.
parseText :: Parser String
parseText = manyTill anyChar $ lookAhead (try (string "//"))
Without try, if I give it an input with a single slash, like
"some/text"
It stops
Michael Mossey wrote:
> Here's what I have so far. It works, but it's a bit weird to consume the
> // as part of the text rather than the keyword. That happens because the
> try( string "//" ), which is part of the end arg to manyTill, consumes
> the // when it succeeds. But maybe it is the most na
Jason Dusek wrote:
2009/04/17 minh thu :
2009/04/17 Michael Mossey :
I wonder how I can get the manyTill to be happy with eof
before finding the //? I tried
parseText = manyTill anyChar (try (string "//") <|> eof)
but got a type error.
You can use 'notFollowedBy' [...]
You get a type e
2009/04/17 minh thu :
> 2009/04/17 Michael Mossey :
>> I wonder how I can get the manyTill to be happy with eof
>> before finding the //? I tried
>>
>> parseText = manyTill anyChar (try (string "//") <|> eof)
>>
>> but got a type error.
>
> You can use 'notFollowedBy' [...]
You get a type error
My confusion is that text is by definition followed by // or eof.
minh thu wrote:
You can use 'notFollowedBy' (probably with 'many1' and 'try').
Something like (untested):
notFollowedBy (try $ string "//")
Thu
2009/4/17 Michael Mossey :
Here's what I've got so far.
-- Text is considered ev
You can use 'notFollowedBy' (probably with 'many1' and 'try').
Something like (untested):
notFollowedBy (try $ string "//")
Thu
2009/4/17 Michael Mossey :
> Here's what I've got so far.
>
> -- Text is considered everything up to //. However, the problem
> -- is that this consumes the //.
> parse
Here's what I've got so far.
-- Text is considered everything up to //. However, the problem
-- is that this consumes the //.
parseText = manyTill anyChar (try (string "//"))
-- Because the // is already consumed, parseKeyword just grabs
-- the available letters.
parseKeyword :: Parser String
pa
2009/4/17 Michael P Mossey :
> I want to write a parser that can read a file with this format: the file has
> sections which are demarcated by keywords. Keywords always begin with two
> forward slashes and consist of letters, digits, and underscore. The text can
> be anything, including special cha
I want to write a parser that can read a file with this format: the file has
sections which are demarcated by keywords. Keywords always begin with two
forward slashes and consist of letters, digits, and underscore. The text can be
anything, including special characters. For instance:
//keywor
Toby Hutton wrote:
> One of the tricks I found early on is to understand where to use 'try'
> (since by default input is consumed even if a parser fails) but apart
> from that just read Daan's page, even though it's out of date, and
> look at how all these cool combinators work.
>
> http://legacy
On Wed, Dec 24, 2008 at 9:22 AM, Erik de Castro Lopo
wrote:
>
> My next problem is matching things like:
>
> identifier ('.' identifier)* ('.' '*')?
>
> I've had a look at lookAhead from Text.ParserCombinators.Parsec.Combinator
> but I can't get it to work.
* is analogous to the 'many' combi
Benedikt Huber wrote:
> Using sepBy1, the above parser can be written as
>
> dot = T.dot lexer
> qualifiedIdentifier = sepBy1 identifier dot
My next problem is matching things like:
identifier ('.' identifier)* ('.' '*')?
I've had a look at lookAhead from Text.ParserCombinators
Benedikt Huber wrote:
> have a look at the module Text.ParserCombinators.Parsec.Combinator.
> Those functions should help you to build up parsers from smaller
> building blocks.
>
> Using sepBy1, the above parser can be written as
>
> dot = T.dot lexer
> qualifiedIdentifier = sepBy1 i
Erik de Castro Lopo schrieb:
Erik de Castro Lopo wrote:
qualifiedIdentifier :: CharParser st [ String ]
Ahh, figured it out myself:
qualifiedIdentifier :: CharParser st [ String ]
qualifiedIdentifier = do
i <- identifier
r <- dotIdentifier
retu
Erik de Castro Lopo wrote:
> qualifiedIdentifier :: CharParser st [ String ]
Ahh, figured it out myself:
qualifiedIdentifier :: CharParser st [ String ]
qualifiedIdentifier = do
i <- identifier
r <- dotIdentifier
return (i : r)
where
Hi all,
I'm rather new to Haskell and I'm diving right into the deep end
writing a parser using Parsec.
In particular I'm using Text.ParserCombinators.Parsec.Language to do
some of the heavy lifting and have this:
import qualified Text.ParserCombinators.Parsec.Language as L
import qual
Dave Tapley wrote:
I find it's good for the soul to remember what the do notation is
doing for us.
Also I'm with Einstein on "You do not really understand something
unless you can explain it to your grandmother" :)
Personally I think (in this instance) your three 'Parser a' functions
read nic
Tillmann Rendel wrote:
My self-defined monadic combinator of choice to use with parsec is
a >>~ b = a >>= \x -> b >> return x
It works like (>>), but returns the result of the first instead of the
result of the second computation. It is kind of an alternative for
between:
between lpare
On 6/21/07, Jules Bean <[EMAIL PROTECTED]> wrote:
I would write
primary = PrimaryIdentifier `fmap` identifer
<|> PrimaryLiteral`fmap` stringLiteral
(I prefer fmap to liftM but they are the same for monads). To my mind
this fits the general pattern of 'constructor comes before content
Levi Stephen wrote:
newtype Identifier = Identifier String
newtype Literal = StringLiteral String -- to be extended later
data Primary = PrimaryLiteral Literal | PrimaryIdentifier Identifier
primary = do {
i <- identifier;
return $ PrimaryIdentifier i; }
<|> do {
l <- s
Thomas Conway wrote:
p `with` f = p >>= (return . f)
so I can write
primary = (identifier `with` PrimaryIdentifier) <|> (stringLiteral
`with` PrimaryLiteral)
I would write
primary = PrimaryIdentifier `fmap` identifer
<|> PrimaryLiteral`fmap` stringLiteral
(I prefer fmap to liftM b
On 6/21/07, Dave Tapley <[EMAIL PROTECTED]> wrote:
> primary = (identifier >>= (return . PrimaryIdentifier)) <|> (stringLiteral
>>= (return . PrimaryLiteral))
> identifier = (many1 letter) >>= (return . Identifier)
> stringLiteral = (char '\'') >> (manyTill anyChar (char '\'')) >>= (return .
St
I find it's good for the soul to remember what the do notation is doing for us.
Also I'm with Einstein on "You do not really understand something
unless you can explain it to your grandmother" :)
Personally I think (in this instance) your three 'Parser a' functions
read nicer as:
primary = (i
On Thu, Jun 21, 2007 at 03:34:54PM +0930, Levi Stephen wrote:
> Is there a way through combining types/parsers that the double do
> block in primary could be avoided?
>
> I understand it's necessary right now because the parsers identifier
> and stringLiteral return different types, so I can't jus
Hi,
Fairly new to Haskell and trying some parsec. (Also, new to
parsers/interpreters)
I had come up with this, which works, but I can't help thinking there's
a better way :)
|> newtype Identifier = Identifier String
newtype Literal = StringLiteral String -- to be extended later
data Primar
Malcolm Wallace wrote:
Andrew Coppin <[EMAIL PROTECTED]> writes:
Any hints?
wholething = many comment
comment = do
fmap Left $ (linecomment `onFail` nestedcomment)
`onFail`
fmap Right $ noncomment
Haskell: The language of truely scary people(tm) :-}
Th
Andrew Coppin <[EMAIL PROTECTED]> writes:
> I have a parser that recognises single-line comments, and another that
> recognises multi-line comments. What I'd like to do is make a big parser
> that returns [Either String String], which all the comments in one side
> and all the rest in the other
Greetings.
I'd like to write a parser that takes some Haskell source code and
seperates it into two piles - comments, and everything else.
I have a parser that recognises single-line comments, and another that
recognises multi-line comments. What I'd like to do is make a big parser
that retu
despite SourcePos being abstract, it can be fully manipulated using newPos.
Thanks for the tip, I thought it wasn't exported.
Gerd M wrote:
I'm trying to use parsec for parsing a custom input stream. As far as I
understood the manual correctly I need to define the primitive parser:
type M
Hi Gerd,
despite SourcePos being abstract, it can be fully manipulated using newPos.
import Text.ParserCombinators.Parsec.Pos
If you can compute the positions from your Tok-stream then you may
consider using "tokenPrim" and work with "GenParser Tok () a"
HTH Christian
Gerd M wrote:
I'm tryi
Am Montag, 9. Januar 2006 12:52 schrieb Gerd M:
> I'm trying to use parsec for parsing a custom input stream. As far as I
> understood the manual correctly I need to define the primitive parser:
>
> type MyParser a = GenParser (SourcePos,Tok) () a
> mytoken :: (Tok -> Maybe a) -> MyParser a
> myt
I'm trying to use parsec for parsing a custom input stream. As far as I
understood the manual correctly I need to define the primitive parser:
type MyParser a = GenParser (SourcePos,Tok) () a
mytoken :: (Tok -> Maybe a) -> MyParser a
mytoken test
= token showToken posToken testToken
where
On Tue, Apr 19, 2005 at 09:47:22AM +0200, Ketil Malde wrote:
>
> Hi,
>
> I've started using Parsec for my parsing needs, and must say I'm very
> happy with it. There is one thing that I'm struggling with
> implementing though.
>
> Basically, I want to parse a file containing multiple records.
Hi,
I've started using Parsec for my parsing needs, and must say I'm very
happy with it. There is one thing that I'm struggling with
implementing though.
Basically, I want to parse a file containing multiple records. I
already have a parser for a single record, and of course I could parse
the
On Sun, Mar 20, 2005 at 03:32:38PM -0500, Dimitry Golubovsky wrote:
> type TParser a = GenParser Token (FiniteMap String Declaration) a
>
> The FiniteMap (which is the user state) is expected to be updated during
> parsing whus building some internal lookup table.
>
> and in one of the parsing f
Hi,
I am trying to develop a parser with the Parsec library. At some point I
need to do something with parser state, say, convert it to a string.
I declared the type for the parser:
type TParser a = GenParser Token (FiniteMap String Declaration) a
The FiniteMap (which is the user state) is expect
On Fri, Nov 19, 2004 at 02:56:38PM -, Bayley, Alistair wrote:
> I've also used Parsec for separated lexer + parser and currently have
> something like this to invoke them:
>
> testParse inputString = do
> case (parse myLexer "" inputString) of
> Left err -> fail ("lexical error: " ++ err
TECTED]
> Sent: 19 November 2004 14:28
> To: [EMAIL PROTECTED]
> Subject: [Haskell-cafe] Parsec question
>
> Hi,
>
> I'm porting a parser over from an OCamllex/Ocamlyacc version and I'm
> using Parsec for both the tokenizer and the resulting token
> stream parser.
On Fri, 19 Nov 2004 14:28:07 + (UTC), John Goerzen
<[EMAIL PROTECTED]> wrote:
> Hi,
>
> I'm porting a parser over from an OCamllex/Ocamlyacc version and I'm
> using Parsec for both the tokenizer and the resulting token stream parser.
>
> I have both of them working fine, but now my question is:
Hi,
I'm porting a parser over from an OCamllex/Ocamlyacc version and I'm
using Parsec for both the tokenizer and the resulting token stream parser.
I have both of them working fine, but now my question is: how do I
combine them? I can't quite figure out how to say "take the output from
this GenP
On Wed, Feb 18, 2004 at 10:48:39AM +, Graham Klyne wrote:
> [To Haskell-cafe...]
>
> At 16:57 17/02/04 -0500, Andrew Pimlott wrote:
> >On Tue, Feb 17, 2004 at 07:48:52PM +, Graham Klyne wrote:
> >> [[
> >> notMatching :: Show a => GenParser tok st a -> GenParser tok st ()
> >> notMatching
[To Haskell-cafe...]
At 16:57 17/02/04 -0500, Andrew Pimlott wrote:
On Tue, Feb 17, 2004 at 07:48:52PM +, Graham Klyne wrote:
> Thanks! That got me going, though not with quite what you suggested.
>
> I ended up with this:
> [[
> notMatching :: Show a => GenParser tok st a -> GenParser tok st
Thanks to Tom for his interesting points. I am still developing an
inuition for how the error reporting goes. (-:
On Thu, 1 Jan 2004, Derek Elkins wrote:
(snip)
> > > testOr3 = do{ try (string "(a"); char ')'; return "(a)" }
(snip)
> example both issues come up. If we successfully parse the
>
On Wed, Dec 31, 2003 at 07:21:54PM -0500, Mark Carroll wrote:
> I tried posting this before but, from my point of view, it vanished. My
> apologies if it's a duplicate.
>
> In http://www.cs.uu.nl/~daan/download/parsec/parsec.html we read,
>
> > testOr2 = try (string "(a)")
> > <|> strin
On Wed, 31 Dec 2003 19:21:54 -0500 (EST)
Mark Carroll <[EMAIL PROTECTED]> wrote:
> I tried posting this before but, from my point of view, it vanished.
> My apologies if it's a duplicate.
>
> In http://www.cs.uu.nl/~daan/download/parsec/parsec.html we read,
>
> > testOr2 = try (string "(a)")
>
I tried posting this before but, from my point of view, it vanished. My
apologies if it's a duplicate.
In http://www.cs.uu.nl/~daan/download/parsec/parsec.html we read,
> testOr2 = try (string "(a)")
> <|> string "(b)"
>
> or an even better version:
>
> testOr3 = do{ try (string "(a")
Hi there,
I'm hacking together a small parser for a subset of C++.
I'm in trouble with left recursion as you may guess.
What is the best way to write a parser for the part of grammar below in
Parsec?
Declarator
-> Name
-> PtrOper Declarator
-> Declarator '(' ArgDeclaratio
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