[antlr-interest] Need help regarding lexer

[elango m]

I got it. Thanks Gavin for explaining so well.

Regards,
-EM-

On Thu, Mar 20, 2008 at 12:21 AM, Gavin Lambert <antlr at mirality.co.nz>
wrote:

> At 05:08 20/03/2008, elango m wrote:
> >I am just curious why STR_LITERAL : '\'' ('\'\'')* ~('\'')* '\''
> >; didn't worked???
>
> Because order is significant.  If you expand out each element of
> that rule and see what it means:
>
>   '\''     : match a single quote
>   ('\'\')* : match zero or more sets of two single quotes
>   ~('\'')* : this is actually illegal, but in theory it's "match
> zero or more characters that aren't single quotes".
>   '\''     : match a single quote
>
> Follow that through in order, and it's obvious why it can't
> possibly match input such as "'a''bc'".  It could, however, match
> something like "'''''''''abcd'.
>
>
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