[antlr-interest] Understanding lookahead
Terence Parr
parrt at cs.usfca.edu
Mon Jun 18 00:35:25 PDT 2007
On Jun 18, 2007, at 5:29 PM, Gavin Lambert wrote:
> At 12:16 18/06/2007, Terence Parr wrote:
> >On Jun 18, 2007, at 9:01 AM, Oliver Zeigermann wrote:
> >> which I was hoping would introduce backtracking which should
> >> have made your example work. Indeed, that option inserted some
> >> code, but IMHO totally meaningless and without effect.
> >>
> >> Maybe this does not work for the lexer?
> >
> >I've never tried it in the lexer...I'd suggest avoiding it even if
> >it works. ;)
>
> Lexer backtracking doesn't appear to work at the moment, but it is
> currently my #2 most wanted feature :)
Lexer backtracking works no problem. Just the backtrack=true option
apparently has a problem. Use (..)=>
> (I also think that the lexer should backtrack by default even
> without any options and without having to make the parser backtrack
> too. The behaviour of the lexer just makes more sense to me that
> way. But I've said that before.)
I think one wants LL(*) by default. Lexers should be mean and lean
by default as they are most of the parsing time.
Ter
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