[antlr-interest] Setting Lexer (Was: Please HELP!!!)
Terence Parr
parrt at jguru.com
Thu Feb 6 23:53:02 PST 2003
Hi Craig...if you're walking over the input more than once, it's
typical to build a tree or some other intermediate form and then walk
that.
Regards,
Terence
On Thursday, February 6, 2003, at 11:40 PM, Craig Main wrote:
> Hi All,
>
> Is there any way of getting the lexer to restart from a particular
> point,
> and consequently, to get the current position of the lexer.
>
> If I need to parse a section of code several times, how would I do it.
>
> Given
> [foreach 10]
> this
> test
> [endfor]
>
> I want to parse this section 10 times. I would use some sort of
> artificial
> stack to keep track of the sections for nesting purposes. I need the
> parser
> to remember where it is at [foreach 10] and re-parse from there 10
> times
> when it gets to [endfor].
>
> Thanks
> Regards
> Craig
>
> On Thu, Feb 06, 2003 at 02:17:17AM -0000, rmsanjivp
> <rmsanjivp at yahoo.com>
> wrote:
>> MyLexer lexer(some istream object);
>>
>> then there is no way for me to specify the lexer to read from
>> different input stream.
>>
>> Is there a way to change the input to lexer while I am parsing? Like
>> telling lexer to read from one file initially and then from another
>> file without re-instantiating the lexer?
>
> a) check the includeFile example (if you want include file like
> behaviour)
> b) check LexerSharedInputState.hpp (if you just want to reinitialize
> after
> a parse run) something like this:
>
> ifstream file;
>
> ....
>
> antlr::LexerSharedInputState lex_input = lexer->getInputState();
> lex_input->initialize(file, filename);
>
> // and reset parser (antlr) internal state
> parser->getInputState()->reset();
> parser->setFilename(filename);
>
> // start parsing at the 'start' rule
> parser->start();
>
> setFilename's are necessary to get correct errormessages. The
> inputstates need resets to prevent 'funny' things.
>
> Cheers,
>
> Ric
> --
> -----
> +++++*****************************************************+++++++++----
> ---
> ---- Ric Klaren ----- j.klaren at utwente.nl ----- +31 53 4893722
> ----
> -----
> +++++*****************************************************+++++++++----
> ---
> "Evil will always triumph, because Good is dumb." --- Spaceballs
>
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--
Co-founder, http://www.jguru.com
Creator, ANTLR Parser Generator: http://www.antlr.org
Lecturer in Comp. Sci., University of San Francisco
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