[antlr-interest] Re: full LL(K) vs linear approximation?

lgcraymer lgc at mail1.jpl.nasa.gov
Tue Mar 18 10:36:44 PST 2003


"Distraction" may be a better description than "laziness", as I'm 
sure Monty will agree:  ANTLR 2 was implemented hurriedly, and Ter was 
immediately thereafter very actively involved in getting first 
MageLang and then jGuru going. There are a few PCCTS features--like 
full LL(k) and semantic predicate hoisting--that didn't make it into 
ANTLR 2.  Ter has "promised" to make sure that they make it into ANTLR 
3. 

--Loring

--- In antlr-interest at yahoogroups.com, mzukowski at y... wrote:
> It also takes longer to do the analysis for LL(K) than for LALL(K).  
The
> main reason it isn't done is because of laziness; LALL(K) works most 
of the
> time.  The ideal is to detect those situations where LALL(K) fails 
and then
> do full LL(K) analysis.  This has some pretty big repercussions on 
the
> current implementation of the LALL(K) analysis algorithm, which 
needs to be
> reworked anyhow to accomodate hoisting of semantic predicates.
> 
> Speed is also a major issue in the generated parser.  The hybrid 
approach
> will be the best win.  Generating LL(K) decision code is 
straightforward.
> 
> Monty
> 
> -----Original Message-----
> From: Albert Huh [mailto:albert.huh at e...]
> Sent: Monday, March 17, 2003 11:03 AM
> To: antlr-interest at yahoogroups.com
> Subject: [antlr-interest] full LL(K) vs linear approximation?
> 
> 
> does anybody know exactly why full LL(k) isn't done in antlr?
> 
> is it due to speed with larger k-values?  (each decision will take 
k^2
> comparisions as opposed to just k comparisions?)
> 
> is it harder to generate full LL(k) analysis code?
> 
>  
> 
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