[Haskell-cafe] parsec manyTill stack overflow

[Badea Daniel]

I'm using makeTokenParser and buildExpressionParser for
the inner_parser. Thanks for your thoughts, I'll use a 
two-stage parser that looks for /end_section> and stores
tokens in heap and then getInput/setInput to feed the
inner_parser.


--- On Fri, 7/4/08, Jonathan Cast <jonathanccast at fastmail.fm> wrote:

> From: Jonathan Cast <jonathanccast at fastmail.fm>
> Subject: Re: [Haskell-cafe] parsec manyTill stack overflow
> To: badeadaniel at yahoo.com
> Cc: "Derek Elkins" <derek.a.elkins at gmail.com>, haskell-cafe at haskell.org
> Date: Friday, July 4, 2008, 3:29 PM
> On Fri, 2008-07-04 at 15:15 -0700, Badea Daniel wrote:
> > The file I'm trying to parse contains mixed
> sections like:
> > 
> > ...
> > 
> > <start_section=
> > 
> > ... script including arithmetic expressions ...
> > 
> > /end_section>
> > 
> > ...
> > 
> > so I defined two parsers: one for the 'outer'
> language and 
> > the other one for the 'inner' language.  I
> used (manyTill 
> > inner_parser end_section_parser)
> 
> Does inner_parser (or a parser it calls) recognize
> `/end_section'?  If
> not, I don't think you actually need manyTill.  If so,
> that's more
> difficult.  Two thoughts:
> 
> * This design looks vaguely XML-ish; is it possible to use
> a two-stage
> parser, recognizing but not parsing the arithmetic
> expressions and then
> looping back over the parse tree later?
> 
> * If the part of inner_parser that would recognize
> /end_section
> (presumably as a division operator followed by an
> identifier?) is well
> isolated, you could locally exclude it there; e.g., instead
> of
> 
> divison_operator = operator "/"
> 
> say
> 
> division_operatory = try $ do
>   satisfy (=='/')
>   notFollowedBy (string "end_section")
>   whitespace
> 
> (Or reverse the order or notFollowedBy and whitespace).
> 
> jcc