[antlr-interest] Elsa parser

Loring Craymer craymer at warpiv.com
Mon May 22 16:00:14 PDT 2006


Ok, I got curious and took a look.  Elsa is specifically a C/C++ parser
developed in Elkhound, a GLR parser generator (that fits with your
"alternative parses" statement--GLR parser generators are usually described
as selecting from a set of alternative parses).

>From the Elsa disambiguation description (in the "AST disambiguation"
section), it looks like they something equivalent to what syntactic
predicates would do (except they are implemented by hand) when fixing up
ASTs.

The short answer is that GLR parsers are "bottom up" and ANTLR is "top
down", and the behavioral differences are a direct side effect of the
different parsing paradigms.

--Loring

> -----Original Message-----
> From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-
> bounces at antlr.org] On Behalf Of Sohail Somani
> Sent: Monday, May 22, 2006 3:34 PM
> To: antlr-interest
> Subject: [antlr-interest] Elsa parser
> 
> Have any of you heard of the elsa parser?
> 
> What this does is build up a bunch of alternative parses and allows the
> developer to choose an alternative when it is appropriate to make a
> decision (based on semantics).
> 
> Does antlr do something like this? Backtracking kind of does it but you
> can still only have one valid parse at any given time. If it doesn't do
> this, is there a reason to do or not do it?
> 
> Thanks!
> 
> Sohail




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