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Home > Archive > Unix Programming > August 2006 > yacc lex output
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| k.jayachandran@gmail.com 2006-08-31, 7:48 pm |
| hello all,
i'm doing a project for parsing a XML file using yacc and lex. i'm
writing grammar based on the sample xml files.
if there is an error in the grammar, i output the error using yyerror
function. but if there is no error i'm not printing anything. even when
there is no error, i see a lot of blank lines and the screen just
scrolls away.
where does this output come from
any help will be appreciated
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| k.jayachandran@gmail.com wrote:
> hello all,
> i'm doing a project for parsing a XML file using yacc and lex. i'm
> writing grammar based on the sample xml files.
> if there is an error in the grammar, i output the error using yyerror
> function. but if there is no error i'm not printing anything. even when
> there is no error, i see a lot of blank lines and the screen just
> scrolls away.
> where does this output come from
lex's default behaviour is to copy unmatched characters to output, so
perhaps unmatched whitespace is being copied. Try adding a whitespace
eating rule, or using a catchall rule such as:
.. ; /* ignore anything else */
at the end of your lexer definitions. See
http://www.telegraphics.com.au/svn/...r/trunk/lexer.l for an
example of whitespace eating and a catchall that rejects unrecognised
characters.
>
> any help will be appreciated
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| k.jayachandran@gmail.com 2006-08-31, 7:48 pm |
| wow, that's brilliant. that explains a lot. it worked.
thanks
jc
toby wrote:[vbcol=seagreen]
> k.jayachandran@gmail.com wrote:
>
> lex's default behaviour is to copy unmatched characters to output, so
> perhaps unmatched whitespace is being copied. Try adding a whitespace
> eating rule, or using a catchall rule such as:
>
> . ; /* ignore anything else */
>
> at the end of your lexer definitions. See
> http://www.telegraphics.com.au/svn/...r/trunk/lexer.l for an
> example of whitespace eating and a catchall that rejects unrecognised
> characters.
>
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| k.jayachandran@gmail.com wrote:
> wow, that's brilliant. that explains a lot. it worked.
You're welcome. I recommend 'info flex' and 'info bison' when in doubt.
--Toby
[vbcol=seagreen]
>
> thanks
> jc
> toby wrote:
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