[antlr-interest] Re: Layout processing

[lgcraymer]

Daniel--

Ter's busy moving into his new domicile or he would probably answer.  Check out his "preserving token sequence" stuff 
<http://www.antlr.org/article/preserving.token.order/preserving.token.order.tml>; my impression is that may help.

--Loring


--- In antlr-interest at yahoogroups.com, "Daniel Shane" <lachinois at h...> wrote:
> Hi all,
> 
> I'm rather new to ANTLR processing and I was wondering if ANTLR could solve 
> my problem.
> 
> The language that I am trying to parse contains layout characters (mainly 
> whitespaces). As I understand in ANTLR, these layout characters should be 
> handled in the lexer and ignored at the source. The problem is that I would 
> like to keep them in the parse tree without having to sparkle them all over 
> the grammar.
> 
> Would it be possible to override LA() and match() to be able to skip 
> (ignore) layout tokens while at the same time keeping them in the parse 
> tree?
> 
> I know that stated this way, it is ambigous, how can ANTLR, without further 
> information, know where to place the WS in the parse tree? In my example, I 
> would like WS to be "factored" out of rules as much as possible so that they 
> are only present in the body of a rule, not at the start nor at the end of 
> them.
> 
> State that way, there is only one place for every WS present in the instance 
> to parse. Not knowing that much about ANTLR, is there a way to automagically 
> override a certain function to obtain this behaviour?
> 
> My only alternative is to sprinkle (WS)? elements nearly everywhere in the 
> grammar... Certainly there is a better way to do this since this would beef 
> up my grammar by 50% (in characters) and also give me the headache of a 
> lifetime figuring out the right k because of all the optional WS that could 
> happen.
> 
> Thanks in advance!
> Daniel Shane
> 
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