From: Hugh Sasse <hgs@...>
Date: 2005-10-28T19:52:47+09:00
Subject: Re: PARSER for RUBY

On Fri, 28 Oct 2005, puellula@gmail.com wrote:

> Hi,
> can you help me?
> I have to write a parser for Ruby. I had think to use the parser
> generator ANTLR.
> I have find Ruby Grammar, but I have problem with ANTLR for "infinite
> recursion". I have cancel left recursion but I have the same problem :(

You've not removed all left recursion.
        [...]
> simple grammar is:
> 
> 
> // PARSER
> class RubyParser extends Parser;
> options { buildAST=true; }
> 
> 
> program         : compstmt;
> compstmt        : stmt;
> stmt            : stmt1 expr
>                 | ;
> stmt1           : stmt IF
        [...]
>                 | ;
> expr            : ;
        [...]

Just take the if example:

stmt = stmt1 expr
     = stmt IF expr
     = stmt1 IF expr
     = stmt IF IF expr
     = stmt1 IF IF IF expr

I don't know antlr well, but maybe
> stmt            : stmt IF expr
>                 | stmt WHILE expr
>                 | stmt UNLESS expr
>                 | ;

might work better?