[antlr-interest] lexer woes

[Matt Benson]

--- Gavin Lambert <antlr at mirality.co.nz> wrote:

> At 11:35 5/03/2008, Loring Craymer wrote:
>  >> 1) Whether backtracking mode is supported for
> lexers,
>  >1.)  Yes--see calls to prefixWithSynPred() in
> antlr.g
> 
> I think that answer is a little misleading :)
> 
> As far as I know, the "backtrack=true" option has no
> effect in the 
> lexer.  However, backtracking in general is
> supported through 
> adding your own syntactic predicates.
> 
> Note that syntactic predicates can only be used to
> disambiguate 
> between alts in a single rule -- you can't use them
> to distinguish 
> between tokens at the top level.  (If you need to do
> that, you'll 
> have to merge the rules.)
> 

I tell you, with all due respect to Ter, writing the
lexer by hand is looking more and more attractive for
this admittedly fairly weird example.  I am trying to
get into being able to support DWIM syntax in a couple
of project ideas, so (elegant) backtracking in the
lexer is going to be pretty important, I think.

Thanks,
Matt

> 



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