Re: A Simple EBNF Grammar based parser

Dear Chris,


"Chris F Clark" <cfc@shell01.TheWorld.com> wrote in message
> > I needed to write down a lexer/parser for SQL for an RDBMS
> > project. I explored a few compiler generators in Java including
> > JavaCC but I found them quiet difficult to use.
> . . .
> > Can anybody tell me why JavaCC and other parsers require proprietary
> > Grammar definition formats when it can be done using merely EBNF?
>
> There are parser generators that use EBNF (for many dialects of EBNF,
> and there are at least 4 major dialects if I recall correctly). Did
> you look at ANTLR/PCCTS? It used EBNF last I checked.


Thanks for the information. I came across Antlr but did not explore it
thoroughly. I will go through it again.
>
> Now, as to your claim of handling left-recursion, is your parser
> generator LL-based?
Yes, My parser generator is LL based.
> Does it generate a recursive descent parser?
No, my parser is not a recursive descent parser. Actually, it can be used to
generate Syntax Trees by parsing a given string.
> (Some of the text I clipped, suggests that you do generate a recursvie
> descent parser.) If so, then the chances are your left-recursion
> support doesn't actually work, but in fact loops on certain inputs.
There is no possibility of looping with my parser. We have thoroughly tested
it. It runs quiet well for a complete SQL 99 specifications.


Now, is it that generation of a recursive descent parser is not possible for
a Grammar involving Left Recursion? Is it easy to generate AST's for
grammars with Left Recursion.?


Thanks once again for the help.


- Puneet

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