[antlr-interest] Understanding Lexer rules

[Mark Volkmann]

On Feb 20, 2008 9:05 AM, Johannes Luber <jaluber at gmx.de> wrote:
> Mark Volkmann schrieb:
> > On Feb 20, 2008 8:50 AM, Johannes Luber <jaluber at gmx.de> wrote:
> >> No. Rereading the text, I suppose one could be confused about that, as
> >> it isn't as clear as it could be. Is adding "Longer matches are
> >> preferred over shorter matches. If one has two tokens KEY='key'; and
> >> KEYWORD='keyword';, then the input 'keyword' will match KEYWORD, even if
> >> KEY comes first." enough?
> >
> > Does the same rule about matching the maximum length apply when the
> > lexer rules use the cardinality operators (?, * and +)? I recommend
> > adding something about that and not just showing examples with fixed
> > literal values.
>  >
> > In case of a tie in the number of characters matched by multiple lexer
> > rules, does the first one win?
>
> I honestly never thought about that, but I believe that the first one
> has to win, or the "keyword vs. identifier" disambiguation wouldn't
> work. Can you whip up some tests to confirm this with a bigger test set?
> I am short of time. :(

Yeah, I'll do that. I may not get to it until this weekend though.

-- 
R. Mark Volkmann
Object Computing, Inc.