[antlr-interest] Confused about backtracking in lexer rules
Jim Idle
jimi at temporal-wave.com
Sun Nov 16 11:51:34 PST 2008
On Mon, 2008-11-17 at 07:44 +1300, Gavin Lambert wrote:
> At 01:39 17/11/2008, William Rose wrote:
> >What I'm finding is that the lexer starts matching the URL,
> >gets to a point where it can't match the character, then
> ;
> TEXT : (URL) => URL { $type = URL; }
> | ~(COLON | SLASH | HYPHEN | ASTERISK | SPACE | TAB | CR |
> LF)*
> ;
Remember that lexer rules that can effectively match a zero length
string are meaningless. That * would have to be + :-)
To be honest I think that wiki syntax is so bad (I don't even find it
that helpful to marking things up), that a grammar to parser such a
thing is going to be so full of exceptions and hacks that it probably
isn't worth it.
Jim
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